General Pump Hammerhead 18"
It's basically the cheapest surface cleaner with a greaseable rotary spindle. General pump also sells parts. It's usable with your pressure washer just fine, and it will accommodate and give better performance down the road if you get a larger pressure washer.
I used one commercially years ago, was a great unit.
Shop around, they can be had from softwash sites on sale for $300. Also to answer your question, wheels are not important during the pressure washing stage. They are only somewhat useful for transporting and moving around the surface cleaner when not pressure washing.