George has it right. I cross referenced it against the 23C Manual since the lens board area is identical.
The manual states the following:
- Screw Tapp - #4BTx3/8" Long Pan Phillips
- Part/Cat. No. 538-13-12-31 (only useful if ordering from Beseler)
If the hardware store does not have it, then try Beseler. Or maybe someone is scrapping one and can scavenger the part. Or, if you have a friend that is handy with metal working, they could tap it for a regular machine thread.
Thanks to all who responded; the specifics cited by Christopher, Fotch, and George are especially helpful.
I checked the screw earlier this morning; now that I'm not relying on my questionable memory, I note that what I need are apparently 6/32 x 1/4 machine screws. I'll try Lowe's and/or Home Depot later today. If I have no luck, there's always the mail-order alternative with some small-parts supplier.
In over three decades of using my 45 MCR-X, i've lost only the one screw, so getting two or three should be a permanent solution.