How do you carry a spare mag?
I carry HK P30 mags (doublestack) and have tried a number of pouches and have likewise been unhappy about how bulky most of them are.
The best I've found so far is the Mitch Rosen 5DM:
The design allows it to be pulled tight, it provides a curved rather than boxy profile, and the leather construction allows it to fit to your specific waistline curve.
The Raven Concealment double pouch is probably my second choice. Not too bulky, but not a smooth shape like the 5DM and doesn't flex to fit your curves.