Zona Alfa is a small-size skirmish wargame by Osprey Press that takes place in “the Zone,” a irradiated part of Russia (or wherever you want) that is crawling with extra-dimensional weirdos, mutants, and other marauders. This warband, led by the mysterious Doctor Van Wey, was kitbashed together from WWI, WWII, Winter WWII, viking, and sci-fi bits.
Zona Alfa has both competitve and solo play options, as well as “campaign” aspects where you can improve your group with better gear and more hirelings. While not technically a post-apocalyptic game, since society still exists outside the Zone, the terrain and feel lend itself in that direction.
Oh, based on the following then: