Are threr any identifying marks on the wheel anywhere?
As much mods that have been done to these likely someone here will know what can be used.
However, I recall seeing only one "N" with 32 inch wheels in all the years we had the dealership. That was a very long time ago and all I can remember was how odd it seemed to appear. I don't recall what they used and can pretty much guarantee it wasn't 'original". My guess is that you will need to contact some tractor salvage yards and work out that may fit.