If it were me, Id look at a Blackhawk SERPA or maybe a SLS/ALS type synthetic design from Safariland.
See my post from above. If you prefer a shoulder holster(with 2 spare mags or gear on the off-side) then look at the models from Ted Blocker, Galco, Bianchi-Intl, DeSantis, Kirkpatrick Leather, Aker(Comfort Flex), Del Fatti or maybe Lawman Leathergoods; www.lawmanleathergoods.com
For range/outdoor carry; get a top rated Bianchi UM92II holster. It's in OD, black, camo. It's based on the US military M12 pistol holster & it's been around since the mid-1980s. You can tote your big XDm pistol tanker, cross-draw, hip, SAS-leg, or shoulder.
See www.natchezss.com www.uscav.com www.midwayusa.com