The Croatian Šokac SMG
 

Ian covered this in today's Forgotten Weapons podcast. It wasn't made in large numbers but did enter service in the early 1990's, so could easily show up in a T2K campaign.

In short, it was a mechanical copy of the PPSh-41 firing 9x19mm ammo, though it looked rather different externally.

http://www.forgottenweapons.com/croa...rom-the-1990s/

Necessity is the mother of invention.