I recommend you contact "the usual sources" who might have some used, but serviceable parts available. Those being, in no particular order:
GetSno Equipment in Newport, Vt. (East coast Tucker dealer)
Track, Inc in Minnesota (Midwest Tucker dealer)
Snotrans in Weiser, ID. (Re-seller of used snowcats)
Perhaps Minnesota Outdoors as well?
You can also call the factory. They may know of someone parting out a machine, or maybe a company that tends to keep their machines in tip top shape and has some good used parts...