Car mount with charger and speaker for GPS?
 

So I'm thinking about turning my old Sprint Mogul into a GPS for rental cars. That way I can save a few bucks because all the car rental companies charge extra for GPS.

I was thinking there has to be something like this already, and just hoping someone could point me in the right direction for the best one.

Something like a car mount that is not permanent, but sturdy. So I won't have to screw it in or anything, and can easily remove it when I am done with the rental car, but don't have to worry about it falling when I am driving.

It would ideally charge the phone (and connect to the cigarette lighter for power) and also have a built in amplified speaker. That way I could actually hear it when it tells me to turn.

Possibly have an external GPS antenna to connect to it also.

Anyone have any suggestions? I tried a search and the most recent post was from like 2 years ago (or more). I'm hoping someone can give me some more up to date info...