I got the cable from JustForJeeps.com for $54.73 shipped, but I see they have already changed the price to $61.60 before shipping. They shipped quickly and were the cheapest place I found, but this is all I have ever ordered from them, so you may want to shop around given the price change.
The part number for the cable is: 4886308AA
The install was pretty easy with the seat out. The hardest part was finding the rear connection point and then getting the cable hooked to it.
On the passenger seat you have to remove the seat belt clip, then right behind that peel the cover and foam back to see the rear connector. It is back in there a ways, and hard to reach. I used a pair of long needle nose pliers to thread the cable onto it.
This guide was helpful, but did not show the rear connection point:
https://www.4x4xplor.com/seattrack.html
The pictures in this thread are really poor, just thumbnails, but they helped me find the rear connection point the best:
https://Jeep Forum/forum/f9/seat-track-release-cable-repair-512193/
All in, it only took 30-45 minutes, so pretty easy.