Think you're right on the snowmobile parts.
Would not be too hard to build a set if you had access to some trashed out snowmobiles.
The only thing I don't like about a lot of the tracks for sale is that they are 'flat' with no angle on the front so they don't work as well when there are obstructions like a fallen tree or similar. Makes it so you are pretty much limited to clear trails, with an angle in the front like my bombi had, it would climb over pretty much anything.
There used to be a courier (ford mini truck before ranger) near Chicago drive and wilson that had half tracks in the rear. Never saw it move so don't know if it was functional or just a parking lot ornament.