I installed my TomTom GPS with the Ram Ball Mount ($30) from Murphs that is designed to be attached to Murphs KB Risers, which I have on my bike. Ram Ball, Ram Mount Arm and Cradle (total cost including shipping $31.84) from ExpressMounts and I was good to go. Easy install, 15-20 minutes.
Both Murphs and ExpressMounts were excellent with delivery - ordered on Monday, received on Wednesday.