It looks like McKay has uzi FS receivers back in stock. You could maybe ask for one papered as a "pistol" or "other" and then use your parts kit to build it up. Buy a brace adapter for the back and run a pistol brace on it. Have the parts kit barrel breech turned down by a machine shop to fit the barrel ring. You'll also need a semi auto bolt, striker/firing pin assembly, and maybe trigger grip assembly. The existing assembly could be modified but you'll need to weld a block in so the safety can't go forward to the FA position. Also you'll need a front sling mount and rivet. That may require a gunsmith or shop to install. And then refinish. You could probably trade off the parts you can't use, like the bolt, to help with the cost. But I'd say budget about $1000 to cover the receiver, semi bolt and striker assembly, brace adapter and brace, small parts, turning the barrel to fit, and refinish. It isn't too bad to build one up this way. It's just that parts are more expensive than 10 years ago. And you have an option for a pistol brace, which wasn't available 10 years ago.