You might hit it right by putting out the word (as you have here) on the forums where people active in shooting participate. One in particular is the N-SSA board (also in our list, but a different part of it).
I found a Chinese Model 50 (like the Soviet PPSH-41) quite by accident when talking about my Thompson 1927. Of course when I got it we had to put the cutting tourch to it to make it legal; but what you're looking for is out there - it's just a matter of finding it. (And if you find 2, let me know IMMEDIATELY.)