Garmin Nüvi bike adapter

Hi there, I'm looking for an adapter or something like that for combining the regular edge navi holder on bikes with the one of a nüvi 2699 car navi, and its larger knob holder. Sure, there are many mounts for 1 1/8" steerer, but in my mind it would be much more elegant than any big other one!

Any suggestion is welcome, even three times around and over the horizon)

Thanks in advance, Peter