I think the Tanaka bike bug might be the same?
you could try:
Link...... Bike Bug
Drive Wheel $28.00 The Drive Wheel is another item that has been improved on design. The rubber of the drive hub simply deteriorates with age and wear. We have put a neoprene high-speed roller skate wheel (62 mm) over the aluminum drive hub. It wears less, vibrates the engines less and bike goes slightly faster per revolution.