Look at the former Yugoslavian countries. The German right-wing terror group "NSU" is suspected to have used weapons from that area [1], the Charlie Hebdo and Paris terrorists did the same [2].
It is entirely reasonable that, similar to the aftermath of the 90s wars, weapons from Ukraine will turn up in every major conflict zone - especially because the current supply from the Balkan is all 30 years old decrepit shit, whereas Ukraine (rightfully) got the very best of the best of Western weaponry.
The stuff the NSU was using can be bought either at Munich main train station (if you know who and how to ask) or just across the Polish border. They used a single Makarov, mostly. And those were basically available for a 5 DM back when the Soviets retreated from the former DDR.