Have a look at a selection of belts in a clothes store. The fold that captures the buckle is often held in place by a short screw bolt like that, with a matching nut (sometimes the nut is like another short screw with a hollow tubular thread that mates with the first.
Single scis!
Mind?
Electric receptacles (wall plugs), switches, and other electrical terminals often use wide flat screw heads with short threads like this. You might even find some brass screws that would stay polished with handling. Otherwise your picture looks like a custom part.
Any of these a match?
What I need is just the end screw from these 5mm x 60mm Chicago Screws but slot-headed. And in stock.
A “Cicero Handjob”?
Eh, I’m being crude. I’ll let y’all get back to your sex bolts and clip-on nuts and mating screws.
I’d call that a machine screw with a large pattern slotted pan head, and I think it looks somewhat customized. I say you take it to a hardware store and check it with various nuts to find the thread size, if you have no micrometer. It looks about like a 10-32 thread to me.