Working on a Dahon Mu N360 with Belt right now. One option. Could possibly downgrade to a Sram or Nexus internal tran if you were interested.

You can definitely get studded snows that fit the N360. (406 - 20").

In 451 a Mu Rohloff is an option (or a simple Mu Uno w/ Belt). Both come with belts standard. Not sure about availability of 451 studded tires though.