Speedmaster case clamp screw broken help

Hello, my 1999 Omega Speedmaster stopped running, so I opened the case and found that one of the movement retaining/case-clamp screws had broken into two pieces.

I suspect that the threaded section had come loose and was intermittently getting into the movement’s wheels, causing the watch to stop. After removing it, the watch started running again.

What is not clear to me is whether this should be the convex-head or flat-head version. Viewed at an angle, the broken head does not appear perfectly flat, but it also does not look as strongly convex as the illustration in the Omega calibre 1861 documentation.

Does anyone know which version is correct for a 1999 Speedmaster Professional Apollo XI 30th Anniversary, reference 3560.50.00, calibre 1861? I believe the part may be the Omega 107 2553 casing-clamp screw.

Does anyone have a spare available, or know a reliable source for one?

Thanks in advance.

Part number you want is 1073163.

It is not a flat head...

thanks. Cousins lists it as discontinued.