You already have a lot of options for DIY zipper pull replacements. But Make shows off a clever way to make your own using the mouldable plastic called Shapelock.
The process here is pretty easy. You just need a bit of Shapelock and a binder clip. Pour a little bit of Shapelock into a glass, pour some boiling water over it, then mould the plastic onto the binder clip while it's attached to the zipper itself. Once it dries, you'll have your own sturdy zipper pull. Head over to Make for the full details.