Never would have guessed
The thing with STALKER is that very little of the gear they use is blatently "soviet". There's no Gorkas that's for sure. Have a look through the Stalker Wiki http://stalker.wikia.com/wiki/List_of_armors and the Stalker.pl facebook page https://www.facebook.com/StalkerPL?ref=ts&fref=ts for pointers.
If you're going for the cheap/easy route then an M65 (in tan if you can find one) and a pair of blue tracksuit bottoms would be the quickest way to get there (although the Bandit jacket in game is supposed to be leather but similar in style to the M65).
Not to say you can't have fun with it and do a "post apocalyptic Russian" loadout, just that STALKER has a very specific look.