This might work for you driving, but not for everyone.
http://www.desantisholster.com/store...03&itm_index=0
There are others, search for air marshal holsters and you will find a bunch. They are usually designed to have good access while sedated. I would go with whatever you can wear all the time. Best to keep the weapon always in the same spot, less to go wrong when you really need to reach for it.