I found out today that EAA in Florida carries repair parts for the Mark X, Charles Daily, Remington 789, 799 actions and rifles. they are at
1-800-536-4442. 7.62X39 magazine boxes and followers etc are available without scavanging whole rifles.
On another note, for some reason I was playing with a 6.8 AR bolt, and picked up a 357 Sig round and tried it on the bolt face. then I figured out the bolt face is the same, and started thinking about taking a 9MM upper and reaming it to 357 Sig then put in the 6.8 bolt and and....... Darn, another project to play with.
this would work for 40 S&W too, I am not sure what to do for a magazine.