If its like the Kammback fuel filler, there is no off the shelf replacement available. The filler is tapered, with the end that attaches at the top larger than the end that fits in the tank. I had to go down to the auto parts store and buy pieces of two different generic fuel filler hoses, one that fit the top and one that fit into the tank. The bottom piece should fit nicely into the top piece, and I used a hose clamp to hook them together. I don't remember the sizes off hand, but its not too hard to figure out.
My original fuel filler hose had been sitting in gasoline for over 15 years, it was the most disgusting, slimey thing I've ever encountered