-- Last Updated: Nov-01-12 5:16 PM EST --
I asked a similar question earlier this year and someone had a good suggestion... Use clear door protector edging available at any auto parts store (napa, checkers, pep boys ect.) The stuff is usually put on the vertical edge of your door for a bumper/ding preventer.
I used this this summer for a while and it works great and takes a beating. Its about a dollar a foot and it worked for a month or so. It wanted to pull away at the edges where the paddle bent but I just put a couple rubber bands around the edge it and let it sit for a week and it held its shape fine after that.
It would get hooked on weeds so I took it off for deep lake paddling but would put another strip on when I knew I was going to a shallow rocky river for the weekend (like the St croix around here). Not a permanent solution but if you don't want to work with epoxy/glass or only occasionally paddle in shallow/rocky areas its a cheap and easy fix.
It cost me $6 for the summer and my paddle tip is still mint.