not stupid at all-
From past experience- if you only need one or two, it's not cost effective to reinvent the wheel. i needed to makes some ceiling mounted mic stands that were in between the size of anything I could buy. I looked at buying a tap and die for the fine threads used on mic stands. For a fraction of that cost I bought a used stand and just cut it to size and instead of the lower piece threading into my mounting plate, I just welded it. It is still adjustable enough for any changes that I'd need.
While it might have been great to have the tap and die, I've not had a need since, so they'd just be sitting in a drawer
With the specialty thread sizes, to get a decent price you'd need to buy quantities, which would only be practical if you were going to produce for sale
at least that's become my take on things as I look at the odd parts I've accumulated over the years in order to make something myself...
unfortunately, I don't have any of those
or, here's a thought (and you might have some laying around)
http://www.filmtools.com/micadapter.html 3/8-16 is a standard thread size
