City Market used to carry them. But I do know that Steamboat Snowmobile Tours carries them at the base cabin on Rabbit Ears Pass.
If you are coming from the Boat the cabin is on the right approximately in the middle. It'll be your ONLY right hand off of Hwy 40, then turn onto a driveand go a few hundred yards. Park in the lot and walk to the cabin and ask the lady at the counter.
EZEEPEEZEE, if you forget to print them out online