More elaborate mount for Magellan Roadmate 3050T

The included window mount works great in the car, but on the motorcycle I need something stronger. I ordered "Ram" brand mounts which are pretty good but I need the final piece, that interfaces with the actual unit. The included mount uses plastic and I would prefer something stronger because of the rougher ride to make sur eit doesn't fall off. Anyone know of where I can buy a stronger piece that actually touches the Roadmate 3050T and can be bolted to the mounting plate? If not I guess I can fabricate something to hold it.

thanks in advance

joe