Ultimate wheel. OR Unicycle with 28-29" Wheel, dont need high end

I live in Norcal.

These Items would be for my son.

He currently rides a 20" Torker, and I just got him a used 5’ giraffe from Craigslist which he was riding around in about an hour.

I would love to get him a 29ish" wheel cycle so he could cruise with us on his Uni when we are on our bikes.

Plus I know he wants an Ultimate wheel.

Cheap is good, if I could afford expensive I would just go out and buy new. LOL