Stripped C-79 Elcan Retaining Nut
Ref. your post it appears you are in the military, I had the same problem with mine and just went to see the FCS Tech., he gave me a package with 2 screw posts and knobs, these are factory repair parts, this is a class C item so you should have no problem getting them either from your EME sec. be it in the battalion or thru a reserve MSU., I have one spare. Cheers G2.