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.