Welcome to the forum. Springfield website states the following:
Left hand holsters
We do not have a left hand holster for our XD(M)Â® or our XD-SÂ® pistols. There are many holster companies that do manufacture left hand holsters for our firearms. If you would like a list of holster companies please email us at [email protected] or call and talk to one of our customer service representatives @ 1-800-680-6866 Monday â€“ Friday 8:30 through 4:30 CST.
I own 3 XDm pistols: a 3.8" Compact 9mm, a 4.5" 9mm and a 5.25" Competition 45ACP. All three of these fit in the same scabbard that came with the gun. So any open ended holster for any of the XDm series will probably fit your gun.
I carry in a Safariland ALS holster that is NOT open ended. My 3.8" fits easily. My 4.5" fits just barely and the 5.25" is not even close. So, if you are looking at anything pinched down on the end, it will have to be specifically for your 5.25" gun.
Someone suggested getting a custom holster made. That's a good idea and they can use any XDm to form the kydex around as long as they don't close it.
Ask around at your next match and see if anyone there has a suggestion.