I think it is easier to conceal a large weapon with an Inside the Waistband (IWB) holster than with an Outside the Waistband (OWB) holster, so I would begin my initial search in the IWB category.
There are two basic IWB designs. Those with loops or clips on the body of the holster, with the Milt Sparks Summer Special II (SS II) being one of the best known. The other is with loops or clips outboard of the holster body. The Sparks Versa Max II (VM II) is one of the best known of this type. The Theis & Supertuck copy this attachment concept but use kydex and leather.
http://www.miltsparks.com/
Most find the holsters like the VM II to be more comfortable, but very slim people often find these wide spaced loops wrap too far around their waist to be comfortable or practical. Often it is easier to wear a holster that takes up less space like the SS II type holsters.
I haven't seen many complain about the grip of the gun poking them, but getting poked by a thumb safety, hammer, or grip safety of a 1911 is common. If that is the case look for a holster with a tall sweat shield. Three makers that come to mind with a tall sweat shield are
High Noon
http://www.highnoonholsters.com/Product_Line/_Down_Under_Straps/_down_under_straps.html
Horseshoe Leather
http://www.holsters.org/iwb-holsters.htm
Andrews MacDaniel II. This uses a single outboard loop, but takes up very little belt space much like the SS II.
http://www.andrewsleather.com/traditional.htm
Kydex will typically be thinner than leather, but leather is often more comfortable. The hybrid holsters like Crossbreed try to combine the virtues of both, but most have wide space loops.
Expect to try a few different holsters. Most folks have a bunch of holsters. Even if you have a good one, chances are you're going to buy more simply because you hope to find something better.
