As Peter says, the motorbike ones should meet all your needs...after all the M3W really is a 3 wheeled motorbike
The only problem is that they are not cheap and it may be more cost effective to buy a cheap car one which can be replaced if damaged by wet. My brother-in-law laughs at my Garmin Zumo motorbike satnav and uses a cheap car TomTom one clamped inside the screen of his GS and over the past 4 years its shrugged off rain etc. RAM mounts should have something that you can mount the actual unit to the car.
