I have no help for you to replace the wheels, only a suggestion to solve your moving issue .....
I would likely use a dolly/2wheeler/hand truck. New wheels that will actually roll well in the grass will not be cheap,
probably not fit the sockets, and require some serious modifications. The flimsy bottom platform
of the 210 would likely require some modifying with some reinforcement as well.
You could likely pick up a used dolly on craigslist for $20, and use a piece of rope, or a cheap $5 dollar ratchet
strap to secure it when moving it.