Bill, Here is a thread that I started a little over a year ago. I ordered a seat from Overton's. When it came it was much shorter than the original seat and cheap too (quality not price). In the thread someone mentioned a company where you could have one made and better quality,but of course more expensive.
http://wellcraftv20.com/community/sh...ad.php?t=21549
Also here is a picture that was in the gallery section that shows how to add height to the currently available seats. 
Good Luck.
Fred