There are dozens of companies making them now and I've seen them down around $25. I'm not a fan. While having a gun on my hip while in the car is not the greatest for access, this "device" makes it far too visible, it's not that user friendly when it comes to drawing and if you get stopped, you're going to be greeted by the officer's muzzle instead of his face as he's yelling don't move/hands where I can see them/etc.
A few companies make "car jacking" or "driving" holsters. I have a Ross Driving Holster. (I'm not endorsing buying from this company, it's just the first to come up on Google) http://www.ccwsupply.biz/RossM23SPAGE.htm