There is a whole AdvRider sub-forum dedicated to GPS's at,
Lots of answers and probably the best place to search. My particular unit is a Garmin 376C (a lucky and inexpensive find for $150), but it is older and no longer supported by Garmin. Nevertheless, some consider these Chartplotters (276C, 376C, 478, etc.) as the off-roading gold standard because they are tough, have buttons and have big screens. I also use a Ram mount and like the vibration isolation of the rubber they use.
I hope my gps lasts a long time. It works very well.