Check with ATV wheel suppliers. The early Honda ATC three wheelers used a completely rubber rear tire. No wheel. The tire had a steel tube that was vulcianized to the tire. If you've ever seen a original set of Cat Trax you'll know what I'm talking about. All Cat Trax did was find the right size alum. axle,add the right dia. delrin bearings, washers on the ends to hold the delrin in place.

The problem with this system was the steel tube, add salt water and.....

As
it turned out Honda's idea wasn't that good and they stopped using that tire. I don't know who was making that tire but they stopped making it cause there was no demand for it. However people that had these bikes needed some way to put tires on their bikes so someone came out with the wheel you see on the new style Cat Trax.

So look at atv suppliers. You might even check with a Honda dealer. If it's not a Honda part you might learn where they would order it from.