I have a used Garmin 61 mounted to my windshield bag in a weatherproof enclosure. Wired directly to the sled with a fuse and on/off switch so I don't need to worry about battery power and can have it on with the sled off. Lighted waterproof toggle reminds me to shut 'er down at night.

 

I'm a big fan of the Garmin units and especially the Montana versions.

 

Garmin watches have come a long way and would be protected under gear. Easy enough to check every couple junctions [or on the fly] to keep on track.

 

garmin zumo xt used it for 6000 miles last year in all kinds of weather and conditions with no problems.

 

I also use the Zumo xt...I use it on the sled and the street bike. I can't go back to a handheld.