I keep extra-heavy-duty Nylon sewing thread on hand in several colors for repairing Cordura gear, sewing on Velcro, patching belt loops on scabbards and so forth. Got it at the fabric store.
Gorilla glue would also work well on the fabric. Coat both sides inside and out near the end, roll it up, cover with aluminum foil or something to keep the glue from sticking to the clamps, clamp in a vise or with two strips of wood and carpenter's clamps. Might get by with clothes pins to hold it while the glue cures if you used enough of them and smeared a little grease or Crisco on the jaws to keep the glue from sticking to them.