its a licence problem?
can you buy a semi auto rifle in 7,63 Mauser?
just take a Mauser carbine were the the stock is fixed, there are some gunmaker making new mauser carbines and it would be easy for them to fix the stock permanently.

this firm https://www.fineguns.de/mauser-c96-karabiner make first class work , building new carbine's, the action use the M 1932 "Schnellfeuer" magazine

make nice Parabellum carbines too

https://docs.wixstatic.com/ugd/ffc909_7a4a3355cf8748eb8d5e3c06dceb329f.pdf

you can buy an original too but they can be expensive sometimes https://www.hermann-historica.de/de/orig...che_um/l/144715
this one here sold for 28000 euro and some value will go if you welding the stock to the action