He could take the cheap plastic panels and throw some layers of fiberglass over it. I used fiberglass to fix a hole on my kayak like that. It was simple fast and cheap. The fiberglass resin and cloth and everything you need to do it can be bought at Hardware stores and even at wal-mart.
I am all for building everything I can myself. I built my front rack for my bicycle, cost me a whopping $4.00 in materials, and some time to weld it all up. I couldnt see paying a $100+ for a front rack thats built out of a couple dollars worth of material.