I bet it would be easy to buy a used blower, and adapt the parts to fit on a ATV. You could also buy the parts and the engine seperately.
A snowblower is a very simple machine, especially when you don't need the transmission. I mean you have the auger housing, the auger, the impeller, the discharge chute, and the drive pulley. All that when assembled, is attached to the other half of the snowblower by 4 bolts in most cases. All you'd need to do is make a plate to mount the engine on, and......
Man, sorry, I get carried away sometimes, I am supposed to be finishing my next snowplowing newsletter!
~Chuck