Take a look at the Safepacker.
http://www.thewilderness.com/safepac...lment-holster/
It straps to the seat belt and looks like an iPad case. I have a G21 with a light attached, and a spare mag in mine. The beauty is that you can walk around with it in plain sight and no one will give it a second look. While I was living in Virginia, I regularly have one sitting on my lap while commuting by train.