I would think nylon zippers are around enough for them to be common in stores. Most water proof and resistant clothing and backs have nylon zippers. But let me know what you find, I have the same issue, I've got a broken soft top zipper on the jeep I just bought and I want to fix it or put the hard top on before winter really sets in.
DD- 1995 YJ 2.5L, Cat delete, 19lb injectors, 30/9.5r15
Trail Rig- 1994 YJ 4.0L, Rubicon Express 4.5inch lift, 1inch body, D30 Aussie, 33/12.5/r15 Cooper Mud Terrains, front bumper, rocker guards