I just got off the phone with the manager of Bay Propeller, which is one of the largest prop repair facilities on the West Coast. He told me that metric-bore props are not something they sell!
I am shocked. He said that you will likely not be able to find a new, metric-bore prop and that the bore reducer is the best way to go. I asked him about new nuts and he said they also would be hard to find, although they could fabricate something if push came to shove.
Well, I guess you learn something new every day. Maybe your best bet is to go with a larger standard prop and a bore reducer. Regarding the nut, you can buy the Beneteau prop nut and the zinc that goes on that. For additional protection, Boatzincs.com does sell limited clearance shaft zincs that will fit in the very small length of exposed shaft your boat has.