Dale Fricke makes some excellent holsters for AIWB carry (Appendix Inside the Waistband, aka "front carry").
http://dalefrickeholsters.com/products.php
The Zaccheus with a Glock 19 or 26 is surprisingly comfortable and concealable once you're used to it. The Archangel is also comfortable and a bit more consistent in positioning. The "Zack" moves around a good bit, which I like when I'm sitting in the car for a long time - that may be better for being in a wheelchair all day.