Sorry but no aftermarket piston is made for this engine.. you can try the link below to see if they have the OEM piston and it came in two sizes only,STD and .030. Good Luck!!! http://www.sea-way.com/
Pretty cool old motors. It looks like you missed the 50th anniversary model by only one year. I too would say Sea-Way. They have a great supply of NOS parts for the oldies.