Not an answer to your question but I DO like the idea of a wrist mount!
Like you I hop between aircraft. I have an old Garmin GPS90 with velcro on the back but never use it because it isn't much use for a quick glance when engrossed in teaching something. I tried a L00X (and before that an Ipaq) but found that the screen washes-out too much in sunlight and it wasn't very good at finding satellites. A wrist mount would reduce the sun issue but may hide the satellites more.
Had you thought about becoming "medallion man"? i.e. making-up something to hang around your neck so you can just lift it up when needed. Clearly the strap would need to be frangible but you could run power and antenna leads down the strap too - just a thought.
Someone recently was raving about a Navigo - 'might be good for a wrist or medallion mount
How does flymap compare to memory map?
HFD