Looks like you got enough recommendations, but wanted to plug the guy I used, his name is Mike Pelletier,
kanvas@aol.com, (603) 529-3230. I'm going to be having him make me a mooring cover for my boat this spring, and last fall he did a custom enclosure that goes on my bimini top (clear plastic on 3 sides), plus he worked on the foam in one of the seats to make it firmer. The enclosure came out great, he put in touches that I didn't expect and was very reasonably priced.
I think he's in Weare, NH (I followed directions to drop off the boat and completely forgot where I ended up...).