I do Civil War Reenacting, and our unit has a canon on a wooden
carrage. When it needs work on the wheels, every few years, we take
it to an Amish shop in Indianna. They can do rebuilds or make a
complete wheel. I don't know what wood, but it's strong enouigh to
drag that canon around a battlefield all weekend, every weekend thru
the summer. Might try to Google an Amish woodworker. Hope this helps.