Until I got a Milt Sparks SSII for my M&P 45 FS, I used an Alessi Talon IWB holster for Glock 23s and 27s. It was nothing fancy and wasn't designed in a way to tuck the shirt around the gun, just a good high quality leather IWB. The Alessi nylon Talon clip is about half the size of the metal clips everyone else is using. Clipped to the trousers, under the belt makes it almost invisible. Then I tucked my shirt around the butt of the pistol, making sure that I "puffed" it out enough to conceal the pistol. It always worked for me and I never got "made."
Crossbreed makes some good, modern holsters for concealed carry. FIST makes some ultra thin Kydex IWBs, and High Noon makes some concealable synthetic IWBs.
Also, don't overlook an ankle rig such as the Galco Ankle Glove. If you're wearing dress slacks or chinos, your pantlegs should be ample enough to cover a pistol when you stand - just make sure they're long enough to cover the gun when you sit.
There are belly bands that you might at least look at, as well as some new appendix carry options.