Sorry I can't help with dimensions, but here's pics of mine. Unfortunately the boat is long gone.
http://www.wellcraftv20.com/gallery/album02
Mine was a factory option. It came with the Bimini, dodger, and camper sides/enclosures. When everything was installed, the boat was totally enclosed.
Most dodgers are custom made by canvas shops though. I think you'll have to get it custom made.