There's a lot of info on that in the archives here but the short story is probably to call Foss in California, (949) 646-0244. They were the original manufacturers of most if not all of the Ericson rudders and can make a new one with their existing molds less expensively than it would cost anyone else to design, mold, and create a new one.
I have one season on a new Foss rudder on my 32, a slightly improved design from the 1969 original, and it's been all good.