If you wanted to repair it cheap, drill a hole in the pump shaft end perpendicular to the shaft, insert a cold roll pin, then cut a slot on the flywheel nut for the cold roll pin to fit in. This will not be a very long lasting or reliable repair, but will get you out of a pinch if you need to. Of course, the right way is to get the new parts but those are some parts that Kymco is kinda proud of. Is it something you could make at work?
~Josh