I believe there was someone at some point in time selling Systema stuff, not sure if they're doing it at this moment (you may have to wait till next shipment).
However you could probably try to get a challenge kit (without the restricted/prohibited parts) and a Systema compatible receiver in country and you should be good to go.
I know there are G&P receivers that are built for Systemas (M4/16 ones) but I'm not sure if they make MP5 receivers.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE