A few years ago my lovely wife bought a the M41 "bulldog" kit at hobby-lobby and I started but got bogged down with life, work and what have you. Fast forward a few years and in our recent move I got a rather large corner to work on models and I decided to pull the old girl from the stash, and lo and behold the poly caps where missing. I measured the stud and the recess for the cap and after some searching I found an excellent, CHEAP substitute.

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hope this helps someone else!
H.J