I guess they are called chicago studs. They are the one-piece, two-sided studs that used to be very common for adjustable straps. Chicago screws might work, but there are drawbacks. One side has a slot machined into it, which is ahistorical. Also, the come unscrewed when you don't expect them to. The one piece units are easy to remove for adjustment, but stay in place unless you deliberately move them.
Up to now, I have always had a good stash of old ones, taken off of old military leather gear. But I am making some new sword belts, and want to find a source for those things, and had a frustrating experience looking for them on the web. A few places sell them one or two at a time, very dearly, as a specialty item, but the regular supply houses don't seem to carry them. It confuses me, because they are stronger, last longer, and should be easier to manufacture than the threaded kind.
I would not be surprised if they go by another name, and I am just ignorant of it. I tried a great many names in my searches.
Thanks everyone for taking the time to read my rant. I joined here out of desperation to find these things. Looking around the forums, I see people doing some very good work. I think I will like it here.
Max