Yes, zippers are repairable... at any fabric store, you should be able to pick up a set of various zipper pulls (if not just the individual one you need - or just another zipper you can get the pull from).
You may need to cut the zipper near one of the ends, insert the new pull, then lash a couple of stitches to close the small cut you made so the new pull doesn't fall off through the gap there.
They are sometimes sold as tent zipper repair kits, or just zipper repair kits. Nothing a little time with a needle and thread can't cure so long as the actual teeth are fine.