There are these inserts with screws-
https://www.axner.com/threadedinsert...inetknobs.aspx
I didn't get them from Axner, but I'd have no problem buying from them again. I got them from an online ceramic store and they were knurled brass. They looked just like these but were only 35 cents each.
https://www.delphiglass.com/casting-...waAiiJEALw_wcB
Can't find them now of course. :/
I made the knobs on the end of either double dipped 3/16" (like for pandora beads) mandrels or just once dipped 1/4" mandrels. Can't exactly remember. Cleaned them and epoxied the inserts in. They've held up well.
Also, if you're in the mood for cab making, these
https://www.dlawlesshardware.com/diy...ull-parts.html work great. Rough them and the glass up a bit, epoxy and let set. I have the ones on the top row, but mine have no hole. Guess they got discontinued? Just have to be a little more extra careful with the epoxy. You also don't want to get any epoxy in the interior threads. Ask me how i know.