you may be able to get that part from PTP still, or you could find and use one from any PTP sleeper or fx cocker body, or even (i THINK but i'm not 100%) from a micromag.
A CCI feed tube bolts nicely to the holes, as well.
You don't see microcockers for sale very often. Especially not on the cheap.
...'cause bandaid's stuck on me!