I have a Sig P229 and it is an excellent gun, although rather thick across the slide. If you carry it in a leather holster with a belt clip directly over the gun, it will make a significant "bump" on your side because of all the layers stacked up, one on top of the other.
One way to alleviate this is to go with a holster in which the belt clips are offset from the gun so they don't add to the thickness of the gun. Having two belt clips, on either side of the gun, will also give better support and stability than a single belt clip.
You might also consider a kydex holster, such as that made by the company Comp-Tac. The kydex holster body is of thinner material than leather, again reducing thickness of the whole package.
Comp-Tac website
Comp-Tac makes a very popular holster called the C-Tac, which is shown below and sells for $75. It can be adjusted in many different ways to vary the cant angle and how low the holster sits in the waistband.
