fwiw these are the 2 galco iwb and owb i ordered and rec'd:
SIL446B SILHOUETTE HIGH RIDE HOLSTER
SC2-440B SC2 INSIDE PANT HOLSTER
the xdm .45 4.5" slides into them okay but the thumbbreak (both have) looks like it would be quite a lot of work to stretch around the back,
galco's site shows the same product # whether for a 9/.40 or a .45, yet i'm fairly sure my .45 is larger dims than the 9 and .40,
but by how much i don't know - that's the thing.
i plan to buy an xdm 9 3.8" as soon as the one i want is instock locally, but i've been waiting for weeks and haven't seen that yet.
for now i'm planning to not stretch these to go on the .45, i don't even know if i could stretch them that far without damaging something, the snap or such. for now i'm leaving them aside to use with the 9 i get later.
Desantis makes a nearly the same of that OWB holster, and i notice they do give 2different product #'s for that model for a 9/40, vs their product for the .45, so i've ordered the desantis for the .45 now.
DeSantis Thumb Break Scabbard Belt Holster Right Hand Springfield XDM 45 Leather Black
Product #: 756757 DeSantis #: 001BAX1Z0
if you did get that model for a 9 it's this:
DeSantis Thumb Break Scabbard Belt Holster Right Hand Springfield XDM 9, 40 4-1/2" Leather Black
Product #: 749914 DeSantis #: 001BAT5Z0
I owned that desantis for a ruger sr9c not long ago (sold the gun and holster), it was a great product and i had no trouble getting the thumbbreak around the back, so i think this for the xdm .45 will work well.
will post results.