At one time, a lot of the the 1-ton rated van type bread trucks were equipped with 19.5" tubeless tires and tapered-bead rims. They were a direct replacement for the 18" tube type tires, same overall height but with a slightly shorter sidewall. If there's a bakery in your area that's been in business for a long time, check to see if they've got some leftover spare wheels and tires!
Jerry