The aviation department at Tractor Supply has a nice wheel for $15 which, with some brass bushings to adapt to the axle diameter and space one side of the wheel to the yoke, is a perfect fit in the tail dolly. Believe it's their part number 3553230. Sorry, nowhere near the trailer or a Tractor Supply at the moment.
Jim

The solid tire from Tractor Supply is what I replaced my tire/tube with. Didn't know if anyone had tried Nitrogen is why I mentioned that earlier.