MAT-49's are rare and parts are also pretty rare.
PPS-43's/PPSH-41's are fun and running them in 9mm Parabellum is cool. I agree with the aforementioned that PPs-42 folding stocks are rubbish, however the wooden post war ones are good.
Swedish K's are great, but I am partial to Sterlings! I honestly believe it to be the world's most reliable sub gun, though some people dislike horizontal magazine placement. Parts kits are still widely available.
MP-40's are fun and very smooth.
I think your budget will open you up to quite a few options.