What we sell at I.J.S. is not slotted for a "scroover". The male is
vee-shaped in profile. The smooth top is soldered to a decoration,
then secured to a garment through a bound hole by a threaded hex nut.
Highway Patrol and Mariachis are fond of their garment highlights and
these are the means of attachment. Called Chicago Screws, and
available in many sizes and configurations.
Other than that, there are threaded inserts for woodworking, more
than likely too big for the purpose. Still probably a good demo for
what you want. Perhaps a watchmaker could turn out some stock for