Hi Frank, you may or may nor be aware I did this conversion a few years back? I used the starter from a HDJ 100, it is 12volts and 3.5kw, it takes a little modding but nothing serious, the point is I ended up with it for nothing from eBay as it was a bit sore when it arrived, also there are loads around....CHEAP!
did you manage to find these? I am looking for the same. Bought a 12v starter from Wood Auto but that has started giving me issues. Looking for a good used genuine one that I can rebuild with new contacts and brushes etc
also seen some Yanmar ones that match close part numbers on eBay. Not sure how good/how much better than the wood auto ones those are. See below.