That has 12 inch wheels I think- 4 to 5 inch or so diameter? If local Yamaha dealer doesn't have that size available or oderable, then check the farm supply and industrial supply places, the commercial tire dealers catalogs. That tire size is about what some snow blowers use- a lawn and garden supplier with the winter products might have that size for snow Kings in stock now. As for the craziness of using a 2 wheeler in snow? Local college campus will have many of the little scooters on road during snow storms and afterwards before plows get done. Some of them and the bicyclist will have snow tires and chains on.

You do NOT want to put snow-chains on any two-wheeled motor-drived vehicle, if the chain slips loose it can destroy more parts than you will be wanting/needing to replace.

Local dealership

Don't be crazy--you don't drive two wheelers in snow.