Same problem here. I'd love to have one, but it's not exactly high on the priority list of things I can afford. I suppose you could dummy up an AK of some type to look close, but in the end it just wouldn't look right and you won't be satisfied.
No one makes a semi receiver as there really is no market. There's only so many kits available, and once you're past that, you'd have to contend with mag cost, and above all ammo cost. There's probably cases of the stuff sitting in storage in the former East Germany. There was a bunch of it (and the guns) shipped to Africa oddly enough as aid to communist rebels. A few years ago when the Algerians were killing each other on the news, I saw one guy toting one around. It was a trip, but plain as day it was an MP/Stg-44/45. I guess you use what you can find.
Building one would be alot of work. I'd love to get ahold of one though.
Ross