There is only one airsoft SMG; the MP5.
It's available in version both electric and gas and with either bargain basement pricing for non-loaded players & all the way up to stratospheric PTW pricing for those players.
Solid stocks, sliding or folding oes, suppressed or not. PDW sized or with a RAS or integrated silencer, high caps or low, metal or plastic bodies and almost as many bolt on parts as a M4.
Easy to find new and tons of choice for used.
Airsoft, where nothing is hurt but feelings.