So far all of the holsters I have for my full size USPs have fit my Sig X5 9mm with little or no modification.
Safariland 328-93(my preferred CCW for every different pistol I own). No mods and the thumb break sits over the beavertail very nicely.
I just picked up a bladetech from another hide member. I opened up the bottom a little so the muzzle could protrude.
Last year or maybe the year before I even modified a(GASP!!) Serpa so it would fit my sig. All that needs to be done there is relieve the top inside edge so it doesn't push the mag catch and drop your mag. Sorry, I don't have it with me or I would post pics.
Safariland 328-93(my preferred CCW for every different pistol I own). No mods and the thumb break sits over the beavertail very nicely.

I just picked up a bladetech from another hide member. I opened up the bottom a little so the muzzle could protrude.

Last year or maybe the year before I even modified a(GASP!!) Serpa so it would fit my sig. All that needs to be done there is relieve the top inside edge so it doesn't push the mag catch and drop your mag. Sorry, I don't have it with me or I would post pics.