Well who told you the zipper is broken? Dealer, mechanic, buddy?
Often if you loosen the top and let it and the window sit out in the hot sun for a while you can zip it right together then tighten to top back up.
If the zipper is broken, most upholstery shops can replace em.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.