Just over a year ago I decided to splash out on a Garmin Quest sat nav system, I chose the Quest as it was quite small and rugged, and they did a motorcycle mounting kit for it along with the car one (it's also waterproof).
Unfortunately (like many no doubt) I was rather disappointed to discover that the motorcycle mounting kit didn't really offer any ideal way to mount the setup on the motorbike. Searched for ages trying to find one, before discovering the perfect solution, a pair of radiator pipe holders from Focus DIY! Designed to hold pipes to the wall I was thrilled to discover that they would also clamp onto the handlebars of the TransAlp, and whats more the four screw holes intended to fix the brackets to the wall were ideally spaced to hold the Garmin Quest motorcycle mount, result!
Namby Pamby scaredy cats could put some tape on their bars before clamping the pipe holders to them if they really wanted to.