I'm not well versed in the "fanny pack/ waist bag" department. However, search for PlayboyPenguin on this board. He generated a thread about using a concealable pack that doesn't look too intrusive.
Also, would you be open to separating your wallet/keys from your gun? What I've had success with was a bag that's made to fasten underneath your bicycle seat. It's big enough to place my wallet/keys as well as essential emergency tools (wheel truing wrench, allen set, etc.).
If you're open for that, then it would open up the possibility to use a holster of your choice. I'm sure you've already considered this but I thought I'd give it a shot in the dark just in case....