Hey Rick, based on your requirements. I would suggest a GPS like the Garmin GPSMAP 276c, 378 or 478. These are Chartplotters (which you can use on the water or flying) They are NOT touchscreens, you use a rocker 4 position switch and several buttons. kind of hard to type in addresses because you have to scroll through each position to choose the correct character. But besides that, the 276c has a small amount of external proprietary memory, whcih means you can’t load the entire country at one time.
These GPS’s can store 3000 waypoints, 10,000 track points (about 4 days of riding), can display 15 tracks at the same time. Failrly large screen. Lockable mounts available through Touratech. Maps can be City Navigator NT or regular City Navigator (non NT)