I've been searching for a rudder for almost a month now.  There is nothing available.  You'll do better to make a new Scabbard, SS would be ideal.  I've contacted a local fabricator and he told me that he would have to build a form for the rudder and the cost would be over a grand.
 I purchased a piece of 4x8x3/4 marine plywood.  Cut it 6'4" and in 3, 16" wide pieces.  I am laminating them together and will sand/shape it like the original rudder.  Hopefully it will fit a little snugger in the scabbard when I'm done with Fiber glassing  it all.

Chris Karo
s/v Kimberly Marie
Midship 25
Plymouth MA
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