Sorry about the slow response: There's a stomach bug going around and of course our kids have been swapping it about on a democratic basis, so I've been up all night and doing laundry much of the day.
I'm not sure that'll work either: The monowheel has developed with the rider on one side, and I realise now most have their driver straddling the 'motor', so I'll have to think again. I think I'll do some surgery on a plastic figure I have spare and look again when I know better what I'm looking for.
Sorry to waste your time Nic, I'll keep an eye on the website though...