What can I say - I like 1911 pistols but I don't like slotted screws.  For 1911 grip screws I prefer Torx head screws both because of how they look but more importantly, you can tighten and loosen the screw without bending/deforming the slot.

The screw heads should fit most 1911 grips and their diameters range from about 0.270-0.272".

This includes four screws and the Torx key needed - Size T15 if you are curious.

I would highly recommed you use a medium strength thread locker or a single-use O-ring to secure the screws and keep them from vibrating loose.

Note, the Springfield Operator TRP pistol is not included :-)