Try this reputable online retailer
www.kitepower.com.au/collections/kitesurfingBUT if its on your LE and any longer than a couple of mm, then don't bother, sail or even dacron insignia tape will not work, if its stuck on the outside. if you can get a bit of dacron insignia tape (the stuff they cut letters and numbers from for yacht sails) on the inside through the zipper, it might work.
Almost all LE cuts need to be sewn by an experienced sailmaker or repairer (we do these repairs too)