These are the best. There's no magnet to mess with the battery or reception, it's not something that permanently attaches to the car. It can be switched from one car to another or one vent to another. I have been using this for a long time and can't imagine my car without it. Helps with GPS, speaker or Bluetooth calling, or other hands free driving.
Veckle Universal Air Vent Car Mount Holder
$4.99 when you add in code: 68ZVFDU8 during the checkout process.