Depending on your physique, IWB carry of a full size M&P 9 might be uncomfortable and not adequately concealed. Nonetheless, if IWB is the order of the day, a Milt Sparks Summer Special original or 2 should suit your needs as a basic holster (many other holster makers have a version of it); the Sparks Versa Max 2 might be better still; it has an incredible following, and plenty of users report carrying all steel Government model 1911s without issue.
If considering OWB, I still don't think anything beats the tried-and-true pancake for close carry. Take a look at El Paso Saddlery or Lobo Gunleather -- their holsters get excellent reviews and I believe they have belts, too, although in my experience the belt is less significant for IWB versus OWB.