Garmin is pretty much the only game in town.
Some guys do use the units made for car use, but you can have issues with weatherproofing the unit (obviously some ways to deal with that), the direct sunlight washing out the screen (car units have weaker displays), touchscreen problems with gloves on (they work like a smart phone), and software since it is loaded up with stuff for use primarily on the road. The upside is they are really cheap.
Then there's the outdoorsey type units like the Oregon/Montana, and the GPSMAP 64. The latter has been around forever in various iterations, and is probably the most common unit in use in the ORV world. The downside to these sort of units is the learning curve with the software - both on the unit, and on your computer (basecamp or mapsource). They are not user friendly at all. If you don't have any interest in really sitting down and learning how they and their software work, they can end up being just a $250-$500 paperweight. Upside is they are weatherproof, have actual buttons that can be operated with gloves on, and screens that are meant to be used in direct sunlight. You can actually use them just fine on a bright day with the screen backlight off. You also need to buy the software to put on them, or they are just track lines on a screen.
There are also motorcycle-based units that kind of bridge the gap functionally and in build design between the above two, but they can be silly expensive. Not sure I've ever heard of them being used on a sled, but there's no reason why you couldn't. They would have the screen for use in direct sunlight, weatherproof, and a touchscreen that works via pressure so that they work with gloves. These have road/street software on them too, like the first one up above.
I have one of each of these types of GPS. The first one on the list never comes out anymore because it has been replaced by a smartphone; the second one is nice when I'm out and away from civilization on a sled, dirt bike, or hiking, and it (and it's software) and I have made friends; the last one works great within the considerations and limitations while riding a street bike.