@Hyengik I have one more option for you! You should try taking it to a tailor or someone who does alterations for clothing. They can probably stitch it for you quickly and inexpensively. It may not look like it did when it was new, but it will be a permanent repair. Another option is a place that does shoe repair - though admittedly these are getting harder to find as fewer people get shoes repaired! People who specialize in shoe repair - in the United States they are called cobblers - are great at working with harder, and thicker materials like canvas and leather. They are also good at fixing zippers! Give those a shot and see if they can help you out.