629-6 Rear sight screw size

[Jeff423]

I recently bought a rear sight for this gun and I thought it came with the screw - it didn't. Rather than paying $7-$10, I'm sure I've got something that will work. It's currently has a scope mounted on a rail that I don't want to remove to check the size. One of the screws from the rail would probably work but then I'd need one of them.
I'd appreciate knowing the screw size.

 

[Protocall_Design]

It's a #6-48 x .280 long flat head.

 

[Jeff423]

Many thanks!