Krimar Camera in New Jersey has parts like this. Calling him is best. I imagine that Fleenor in California also has some.

If old and grungy is ok, drop me message, with a photo if possible with some sort of scale, like a dime, and I'll see if some I have off of Automats or 'Cords will fit. I know the basic size and hole layout is the same from Automat to E, but I don't know about the F. By the way, the opening is not symmetrical, so show all three screw holes. And any notches or such.