I would recommend carrying an unmounted spare. More places can change than have truck tires. Just get a good used tire to carry.
If you haven't replaced the tires, look at regular truck tires and get drivers for the rear and steer up front. Drivers will gives a little better traction than universal. Also by using truck tires, if you do need to buy, truck tires are more common then RV tires.
Suprised someone didn't mention, when you see those little flags or cones at the side, slow down. Thats indicating road damage. You will see them also in Alaska as well on the hwy. Not all is marked, so be careful between Burwash and the border.