Are there any companies that sell the big-ass glass/ceramic antenna
strain and standoff insulators anymore?

Most of the ham antenna places that sell wire antennas have a single
style of really tiny ceramic strain insulator, and one or two plastic
strain insulators, but they all obviously are made by the same company
and imported. Nothing wrong with them, but the ceramic one really will
not hold any rope above 3/16", and the plastic one won't take any rope
above 1/4" (and even that only with some effort.)

I have been buying good insulating plastics (e.g. G-10, Polycarbonate,
etc.) and making my own insulators, but if there were a good source of
the big classic ceramic and/or glass ribbed insulators - not just
strain but also the standoffs - I'd buy them in a hearbeat.

Cool old insulators do show up on E-bay etc. but they're generally
onesies-twosies and obviously being sold to collectors, not hams who
string them up on antennas.

I can go to the industrial supplier indices and find companies, even
local companies, that custom-make ceramic and glass insulators for the
electrical industries, but they have no intention, or even mechanism
if I call them, of selling a dozen insulators to an individual ham. If
anyone knows of an exception, please let me know!