Photos so we can help you. Really no idea what you are asking.

Are the images of your house?

I am trying to find the matching crosshead to replace the spot the old cross heads are in

The crosshead is a trim piece and it being broken should not allow water in under any circumstances. Post a picture of your house but a broken trim piece that is surface mounted is not where your water is coming in.

millworkman is correct again: "...it being broken should not allow water in under any circumstances."

Finding a match is a much easier problem than diagnosing and curing the mechanical flashing failure that's causing your leak.

Even if the hole allows water to collect during a storm...the water then slowly leaks into the top of the window frame from sitting in the trim?

" .the water then slowly leaks into the top of the window frame from sitting in the trim? "

Still not a pediment problem as this is purely a cosmetic trim piece. The issue is the window installation and flashing (or lack there of).