[R-390] Ungar/Weller(?) Soldering Iron Tips?

[Barry]

A little OT, but does anyone know of a source for the old copper soldering iron tips that have #6-32 threads?  These are for old Ungar heaters.  All of my tips have pretty much disintegrated.  I thought the #824 tips were correct, but I think those are most likely #10-24 (3/16"?).  Not even sure if these are still available.  Worst case, I could probably turn the 824's down and rethread them but that's kind of a lot of trouble...

Thanks,
Barry - N4BUQ