Cannot help you with plastic kayaks, but should you be interested in a custom made kayak, tailored to your fishing needs, go to the following website:
http://www.shearwater-boats.com/About.html
The owner, Eric Schade, does do custom work for designing kayaks from the ground up. He has done such innovated designs as mounting a gear box in boat such that footwork will drive a screw (propeller.) He has put out several kayak designs which integrate an electric outboard into the hull design so you can extend your fishing range ever further than one might imagine. The only complaint I ever heard was that he sometimes does work like Jim, he makes it just too nice. After obtaining one of his designs, you might be tempted to place it over your living room fireplace mantle as a show piece rather than using it. He is also involved in designing kit boats which would allow you quite a bit of freedom customizing the craft to your own specialized fishing needs. He built the commercially registered rowboat that I fish out of. The only argument we had was over price. I knew he underestimated the cost involved for the needed time and materials, so I offered him more than what he had quoted when the project was done. It was a silly type of negotiation in which he refused my top offer, and was bargaining me down while I was trying to bargain him up. Eventually we reached a price for which we could both live with. Eric is a super nice guy to do business with and a great boat builder.