I've been buying these 100 at a time from McMaster-Carr
https://www.mcmaster.com/#57455K51 for a $1.90 each. I'm starting to use
them up quick enough that I'd like to see if buying 250 - 500 might find me
a better price somewhere. I've checked obvious places like Amazon, MSC,
Carr-Lane, and EBAY. Essentra has nearly nothing. Zoro's website is about
worthless when you search for something they don't even have and get 6000+
results. I used Google's site search and most of Zoro's stuff was more than
twice the price.

1/4-20 female insert phenolic handles. I don't want the ones MSC has that
have a formed thread. I want one with a female insert.

They get used on lead, tin, and pewter casting molds, so I don't really want
to get away from the modest heat handling of phenolic. My local screw
vendor doesn't have them. I asked.

Last time I looked around McMaster had the best price, but I was only buying
20 at a time then. Maybe they still do.