OK Since no one else mentioned it I will do it. If your looking for a relatively inexpensive GPS, go for a Garmin NUVI with a good mounting system. Don't worry about that "Waterproof" and "Vibration proof" crap. I can assure you that I've been riding with NUVI's for more then 10 years with absolutely no problems at all, and best of all is that they are cheap and easy to find EVERYWHERE. The Garmin ZUMO is so friggin expensive, it makes no sense... They all use the Same Operating System and other then the before mentioned stuff, not worth it in my opinion. You can buy 8 used or refurbished Garmin Nuvi's for the price of one of those Zumo's. I've been riding with Nuvi's for years and they simply work great in all conditions. If it rains, I usually just toss a bag over it, or just put it away in my pocket. I have mine hardwired into the battery with a hotwire so it turns on with the ignition. No worry about draining the battery or anything.
The new NUVI's have some great features like a tablet, like instant on and horizontal and vertical navigation. Go to RAM Mounts website and look for a nice handlebar solution for mounting and get yourself a nice Nuvi in your price range and ride. Don't give in to that Zumo nonsense, you'll be overpaying for nothing unless you really do ride in the rain for hours and hours at a time and want to navigate in the rain
Alternatively, you COULD use something like an android or iphone for navigation but I find the screens too small and require something other then a glove to operate... Nuvi's work perfectly with gloves.