I love the idea of a special department store for Guards officers!
In the British forces we had the NAAFI (Naval, Army and Air Force Institutes), which initially ran troops' canteens and then branched out into supermarkets - essentially, the British equivalent of the PX. However, that has now gone. The canteens were 'other rank' and the supermarkets all ranks.
Since both Sandor and Colonel Muraviev are suffering from hangovers after the mess dinner, they will be in need of coffee, but I can fit in a few comments about the high price and declining quality, and that one of the few signs of the war at the Stavka is the awful coffee.