If the drive wheel is shot I can help walk you through making one. Do not throw away the aluminum core from the old drive wheel as you will need it for your fabricated replacement. Neither the drive wheel or even the core are available now. Not a problem, though. Google Tanaka and you can find the company in the US and also Mike Snyder's web site. I think there are also a few articles as well.
SB

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Someday when I grow up I will probably lose interest in toys with wheels, but until then...