A steel screw of the proper thread (if difficult to find a brass one online) could be
- cut to desired length
- rounded off for easy "starting"
Then...
A FUBAR (bent-threads Conn/King/etc. bell screw could have it's FUBAR threads cut off, the center of the knurled head drilled out, the hole threaded to the Holton threads, the steel screw threaded into the salvaged brass knurled head, silver brazed in place, and then cleaned up.
If (even) a "free" screw is desired, MOTORCYCLE customizing addicts (there seem to be some in every town) usually have huge amounts of odd-thread/seemingly-proprietary thread sizes of screws (bolts) in this size range.
These are suggestions for POSSIBLE local solutions, without buying anything and without needing a lathe.
If (??) this suggestion is viable, you might need to pay a repair guy to braze and buff the knurled head, though...OR buy them a cheeseburger, fries, and a coke.
ALL OF THAT
crap having been typed...
IF (??) it's one of these two goofy sizes, Ferree's offers these:
(question to the TFFJ: Are these the sizes for Olds/Reynolds and Holton, or something else?)
C75KB 1/4-28 thread (brass)
C75KN 1/4-28 thread (nickel)
C75LB 1/4-24 thread (brass)
C75LN 1/4-24 thread (nickel)
Sku: C75HB