I've got a couple old skinny shafts with a 5/16-14 flat faced joint; brass inserts.
It's hard to say what they were made for originally; but, they have dark chocolate phenolic rings at the joint which may contrast well? Old brown phenolic is difficult to match!
One ferrule appears to be old micarta; the other melamine.
Pics are attached - let me know.
Green leaf is NFS