I have "A-cat" AHPC rudders/stocks on my Taipan. They are magnificent and less expensive than you'd think. Check the AHPC web site:

http://www.ahpc.com.au/

Click on the auscat flyer button at the top and scroll down to see the carbon rudders/stocks.

Email AHPC and they'll give you a quote. We all know that Hobie parts are not inexpensive.