Unfortunately you are pretty much out of luck when it comes to wheels for these bikes. I looked extensively for wheels for my 300 KQ with no luck. I had even ventured into the wheel adapter avenue with no success. And welcome to the Forum.
I had some made for my 1990 quad so I could adapt a set of wheels that were originally for my 2013 King Quad. I had a friend that worked at a machine shop. These are 1/2" aluminum rings with stud taps. Had same made for the King Quad to adapt a nice set of Can-Am rims to it.