Not a whole lot of options if you want to run a different tire on the stock 16 inch wheel. But there are a few companies making a 16 inch tire. The other day I saw on Rocky Mountain ATV that the Tusk Tarrabite 35 inch tire is offered on a 16 inch wheel and is $260 ea. The Tarrabite has been around awhile and is a good proven tire.
Here is a picture of a H2 with the 35 inch 16 wheel Tarrabite tires.
Here is a picture of a H2 with the 35 inch 16 wheel Tarrabite tires.