My M&P .45 Full Size is riding in a DeSantis Glock 21 holster....might work for you as well. All major manufacturer do offer a holster for the M&P series. Also check with our fellow members that are vendors on the site. Lobogunleather is one and does a great job like the others listed as well.
Randy
I have Comp-Tac belt holsters for my M&P pistols. The 9mm and 40 use the same belt holster. They are 5 inch Pro models. The 45 has a 4.5 inch barrel and a slightly larger frane. The holsters are made for each gun. The mag pouch used for the 9mm and the 40 is the one made for the Production class. It doesn't fit the 45 acp. I use Uncle Mike's mag pouch for the 45. It's cheaper but doesn't fit as well. The holster is IDPA and USPSA legal. I don't know about the mag pouch for IDPA. It is legal for USPSA Production.