all crossbreed holsters that have XDM as an option work with all lengths of XDM,
Comptac makes an Mtac minotaur holster for the 5.25 as well as an outside wasteband holster. found all that in about 3 minutes.
Besides the barrel length, the gun is the same as the standard XDM. Most holsters accommodating the XDM will have an open muzzle end, so it would be perfectly compatible with the 5.25.
I have a holster from firearmholster.com and it's excellent. Really good price and very well made. It's a hybrid style IWB. Alien Gear is also a good option.
Check out Alien Gear holsters. I've got three and love them. They make to order and have a 4+ week shipping but with lifetime replacment, 30 day money back no questions and a free lifetime shell swap if you ever change your EDC.