Yeah thats sort of the trouble here. My boat, Wauquiez Amphitrite 43, was built in France
and they used wonderful bronze thru hull
fittings but the threads are BSPP which have a different thread angle than NPS and of course are straight threads so NPT is out of the question. I have a machinist friend who has the ability to cut BSPP threads so we may end up making our own caps but I was hoping with a little research
to find some off the shelf. Mcmaster Carr typically great for this sort of thing are of no help.