I was looking for a 12 inch rear wheel with sprocket and axle, but couldn’t find many on eBay available to Australia. It looks like a lot of the models which take those wheels never made it to Australia (maybe due to being too high powered?).
I found a whole electric scooter for sale for less than the cost of importing a single wheel! Ideally this will a 450W MY1018z chain driven to a 12″ wheel and I can steal most of that for the unicycle. I’m expecting it to really be a belt drive 200W MY1016z, but as long as the wheel/axle/wheel mount is good I should be able to put on a sprocket and then chain drive it from a new MY1018z.
I’ll find out when I pick it up!