Here is the one I use:
Its a Scosche brand has a solid suction cup that mounts to the windshield with a flexible neck that is long enough to get the Pre down out of the way of your view of the road. I have mine down where I can get the A.C. vent pointed at my Pre so it doesn't get sun backed on the really hot Texas summer days. As you can see the hold arms have a curved open design that accommodates the Pre charging cord and still allows the my Pre to be removed from the mount without having to disconnect the charge cable. The only issue I have had with this mount is that it vibrates when I hit a bump or general road vibrations will cause the Pre to shake I have solved this issue by bending the neck down so that the back of the mount is touching the dash board this helps the mount and keeps it from shacking. I purchased this mount from Fry's electronics.