All material and reconstructions are from A. Karevskiy, unless otherwise noted.
According to all available information, the banners of the Holy Cross Brigades were largely copies of church banners, and sometimes they were even used directly. In his article, I. Eyngorn emphasises that in battle, "clergymen marched in front of the militiamen, singing prayers and carrying banners".
Eyngorn, I. in "Union of Unfulfilled Hopes: The Church and the Counter-Revolution in Siberia //Science and Religion, No. 2", 1997, pp.23-24.

An advertisement in the newspaper Russkaya Rech dated 17 September 1919 requesting assistance in sewing a banner of the Order of the Holy Cross
The advertisement lists the colours of the fabrics considered essential for making the banner:
Help the crusader militia!
Silk fabric in blue, light green or light blue is urgently needed for the crusaders' banner.
Or a silk shawl with tassels.
Address: Lashkova, No. 4, Chairman Drobinin.
"Russkaya Rech, No. 200 (273)", 17 September 1919. Material kindly provided by Voronezh researcher N. Zayats.
On 3 September 1919 the Omsk newspaper Nash Put reported that the Old Believer community of the city was "embroidering a silk banner with the image of Christ Not Made by Hands for the Old Believer Crusaders".
"Old Believer gatherings in Omsk // Nash Put, No. 9", Omsk, 3 September 1919. Quoted from "General Diterikhs", Moscow, 2004, p.325.
On 25 September 1919, the same newspaper reported that "The consecration of the Crusaders' banner will take place in the Old Believers' prayer hall (corner of Irkutskaya and Zavodskaya) at 10 a.m. on 27 September."
"Nash Put", Omsk, 25 September 1919. Quoted from siberia.forum24.ru/?1-4-0-00000029-000-10001-0).
Below is a reconstruction of the banner of the Omsk Brotherhood of the Holy Cross for September 1919, made from photographs from the State Archive of the Russian Federation (in the book "General M. K. Diterikhs"), and for the front using descriptions by the Moscow researcher V. Zh. Tsvetkov.

Banner of Omsk Brotherhood of the Holy Cross

The reverse of the Omsk Brotherhood of the Holy Cross banner
www.museum.vladimir.ru/katalogy/italia/P2/34000018?menu=katalogy/italia/m_2_2
"General M. K. Diterikhs", Moscow, 2004.

Saviour on cloth. Late 16th century
From the collection of the Suzdal Museum of History and Local Lore
This image is given as an example of old Russian embroidery, the tradition of which was preserved in Old Believer communities. Something similar in composition can be seen in footage from newsreels of a parade of White Army troops in Tomsk in the summer of 1919. The third banner appearing is quite large, clearly larger than regimental banners, with a wide dark border and an image of the Saviour in the centre.
Photo from www.museum.vladimir.ru/katalogy/italia/P2/34000018?menu=katalogy/italia/m_2_2.
Video published at community.livejournal.com/warhistory/1946555.html?view=33775291#t33775291.

Presumably, the banner of the Virgin Mary Regiment
From the book "Crusaders: Kolchak's Last Reserve"
A silver brocade banner. In the centre of the front there is a cotton rectangle with an image of the Blessed Virgin Mary, edged with a narrow golden brocade ribbon. The reverse side has no images or inscriptions. The lower edge of the banner is trimmed with a brocade ribbon with two tassels and fringe. It is stored in the banner collection of the Central Museum of the Armed Forces in Moscow.
Karpov, N. D. in "Crusaders: Kolchak's Last Reserve", Moscow, 2014.

Presumably the banner of one of the Holy Cross Militias.
From the book "Crusaders: Kolchak's Last Reserve"
The banner is made of white cotton fabric trimmed with a cloth fringe. The lower edge is cut into three pointed "tails". On the front side, there is a frame for an icon with crossed laurel branches above it. On either side of the border is the inscription: "Christ is risen". The letters "Х В" (for "Christ is Risen") are placed on the right and left tails. On the middle tail there is an image of a crossed anchor, a cross, a wreath and a heart. All three tails have a six pointed star at the bottom. On the reverse is the inscription: "You are a priest forever, in the order of Melchizedek". The letters "Х В" are placed on the middle tail, and the letters "НИ" and "КА" are placed on the right and left tails. All images and inscriptions are made with a chemical pencil. It is stored in the banner collection of the Central Museum of the Armed Forces in Moscow.
Karpov, N. D. in "Crusaders: Kolchak's Last Reserve", Moscow, 2014.

Presumably the banner of the Michael the Archangel Regiment.
From the book "Crusaders: Kolchak's Last Reserve"
The banner is made of white cotton fabric, trimmed with cloth fringe. It measures 123 by 78 cm. The lower edge is cut into three pointed tails, and there are three tassels at the ends. On the front is an oil painting on a piece of canvas depicting a half-length image of Archangel Michael and an inscription: "Archangel Michael rules the path of victory, brave and with a spear and a white banner in his right hand". On the middle tail there is a monogram in the form of the capital letter "Р". In the centre of the reverse there is a cotton rectangle with a full-length image of Archangel Michael. Around it is an inscription: "All the pride of the evil yoke and the rebellious Lucifer, who fell forever under the foot of the Archistratigos [i.e. Archangel Michael]". All inscriptions are made with a chemical pencil. It is stored in the banner collection of the Central Museum of the Armed Forces in Moscow.
Karpov, N. D. in "Crusaders: Kolchak's Last Reserve", Moscow, 2014.

Reconstruction of the banner of the 1st Omsk Militia of the Holy Cross
Review of the Holy Cross Militia.
Regarding the major victories and the issue by the Supreme Ruler of a letter on the convening of a State Zemstvo Conference, at 1 o'clock on 18 September a national prayer service was held on the square in front of the cathedral.
... After the prayer service, there was a review of the 1st Omsk Orthodox Militia of the Holy Cross and the Muslim "Green Banner" Militia.
The celebration began in the cathedral, before the prayer service. There the consecrated green silk banner of the Holy Cross Militia, with a militia Cross and the words "For faith and fatherland" in gold, was presented to the standard bearer.
"Our newspaper No. 32", 21 September 1919, Omsk. Material courtesy of Voronezh researcher N. Zayats.

Reconstruction of a flag of the Green Banner Militia
The crescent is oriented to the left, modeled after the banners of the Bashkir regiments. However, according to the Moscow researcher V. Zh. Tsvetkov, the crescent moon could also be oriented to the right and depicted without a five-pointed star.
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The original of this page is at kolchakiya.ru/vexillology/sacred_cross_green_flag.htm.