There are many options for this repair.
First, prove that the half moon part is broken or worn off.

If it is, you could have it welded and filed round again.

Or, filed flat, a hole drilled, and a new shaft sweated in, and then filed to length.

It just depends on what facilities and abilities you have, and how you wish to proceed.

Always easier to spend an afternoon calling around to old gun junk yards for the part.
Maybe start on a Savage forum locating parts repositories.

Out there doing it best I can.