Go to the CMP Carbine forum, these guys can tell you every thing there is about the Carbine, including where to get orginal parts.
As far as "bring backs" WWII was a totally different story then today's military. With in reason no one cared if you took your rifle home.
My father told me, after the war people coming home had to pass by several venders on the ramp, on the way to the plane, selling M1s 45s etc. LEGALLY
I got a used sling from CMP to go with my CMP Carbine. It had a name writtnen on the inside. My wife did a search and found there were two people by that name in WWII, one in the Pacficl and one in Europe during 1944.