Hello, You can look on aliexpress or one of the other sites that have zipper insert pins and boxes.   They are very inexpensive and if you can carefully take it off the current zipper, withouit fraying the fabric etc., then you can put a new zipper box on with a plyer.   If it frays would suggest after you receive your zipper boxes and pins, then  reincforcing it by bonding a lightweight nylon material with some sort of adhesive like superglue and then using a sewing machine to add a few stitches for strength.  You may even want to put s little bit of sugru, epoxy or something on the fabric bottom of the zipper to stop any further fraying as well as to bound all layers together.