It's anything *but* a simple swap.
Ginsu's talking about the replica eyes meant to fit in an actual flashgun - not the thumbscrew.
There's no center stem. It's a chrome bezel with a clear acrylic lens. There's also no easy way to attach it to a US Graflex, since the US lacks the threading for it to screw into place.
You *could* use a 10-32 replica-eye thumbscrew, but you'd need to:
1) Remove the acrylic lens
2) Drill a hole through the center of the 10-32 threaded stem
3) Replace the lens
4) Drill/tap a 10-32 hole into your US bladeholder
5) Dremel the heck out of the US faux-button-bezel to accept the replica eye. Or maybe replace it with a 16mm AV bezel. Either way, you need about a 19/32" hole in the bezel to accept the base of the replica thumbscrew.