I made my own kit. I use my Nuvi in several cars but wanted it hardwired and mounted in the 4Runner. The suction cup is fine for the other vehicles.
I used a proclip mount and bought some extra Nuvi parts on ebay. I bought an extra charger and L bracket mount. I cut the male end of the charger so I had the wires and piece that clicked into the cradle. I also cut up the cradle and mounted it to the proclip. It's super solid and always ready to go.
Easy piesey. Took about 30 minutes. I have a blue sea in the dash under the radio. The power wire is plugged into there and comes out of the dash vent right behind the Nuvi. When the Nuvi is not being used the wire tucks into the vent.