There are always places to get parts. You could start with a "wanted" ad on our classified board – ad is free and you don’t have to be a club member. If that doesn’t work, there is always http://www.twincityoutboard.com. They are an outboard junkyard that has over 10,000 motors from 1906 on up. They are just south of Minneapolis, but will ship anywhere, but not the cheapest place in the world. Those SeaBees were made by Scott Atwater and most parts interchange. Motors like that are pretty common and you can probably find a parts motor cheap on Craigslist, ebay or other online place. Careful on putting to many $$ into it – these aren’t worth much fully restored, but you can’t put a price on the fun of breathing new life into it. It was common on motors like that to throw away the lower cowl to allow faster access to the spark plugs.
Dave