I've had this cheap document bag (from some conference) for a few years. The zipper pull had a loop that broke off last week. I decided to try something new. The result is this zipper pull.
Step 1: Tools and Materials
The zipper pull is made of nylon cord with a sleeve of plastic tubing. I used 3mm accessory cord and plastic tubing used for oxygen masks. Any clear (or coloured for that matter) tubing should work. Most aquarium stockist or hardware store should have it. Make sure that the inner diameter of the tubing is close to the diameter of the cord. The fit should be snug but not too tight.
For tools you will need scissors (or a sharp knife), a lighter and a short length of nylon cord that can be pushed through the plastic tubing with ease. It should be longer than the length of tubing you will cut (see later step).
The lengths given here are what I used and worked well for my particular zipper and gives a loop through which a finger comfortably fits. You may want to experiment with different sizes.
Step 2: Cut Cord and Tubing
Cut the accessory cord to a length of 17.5cm (or 7 inches). Cut the tubing to a length of 12.5cm (or 5 inches). The difference of 5cm (2 inches) is about the minimum you need (for 3mm cord) to still get the zipper pull through the eye of the zipper.
You don't need to heat-seal the end of the cord yet.
Make sure that the thin cord is longer (at least 5cm (2 inches)) than the tubing.
Step 3: Join Two Cords
Melt one end of the accessory cord as well as one end of the thin cord and join together. This may take some practice. Be CAREFULL as melted nylon can get very hot and can burn. The joint should be be made fairly strong.
Step 4: Work Cord Through Tubing
Push the thin cord through the tubing. The thin cord should be thin enough to be pushed through easily and long enough to have a decent grip before the accessory cord gets into the tubing.
Slowly pull the accessory cord into and through the tubing. If your melted joint is not strong enough or the fit is too tight you may struggle or the joint may break.
Make sure that the accessory cord stick out at both ends of the tubing (+- equal lengths).
Step 5: Cut Thin Cord
Cut the end of the accessory cord where the thin cord has been joined to it. Again, there is no need to heat-seal the end of the accessory cord.
Step 6: Join Ends
Melt and join the ends of the accessory cord together. Try to make the joint as thin as the rest of the cord. Again, be CAREFULL as melted nylon can be dangerous.
Step 7: Tidy Up
This step is not necessary, but will give the zipper pull a neater appearance and may even be slightly stronger.
Work the joint into the tubing. This may be slightly difficult, depending on how tight the accessory cord fits inside the tubing and how big the joint is.
Step 8: Tie In
Push a loop of the accessory cord through the eye of the zipper. Open loop and push the tubing through this loop. Tighten. Et voila!