I've had good luck with the $50 dollar ropes from Amazon with free shipping. I use them often and they've held up well. Also try your local dealers.
When you unspool the cable and get to the end of it, you will see exactly how it's done. There is a llittle hole in the drum that the cable goes through and an allen screw that tightens down on it.
You can't use the screw with the rope or it will chew it up. You run enough rope through the hole and lay the running end all the way across the drum sideways. Then you wrap 1 or 2 layers of duct tape over it to keep it in place. Hold tension on the rope as you wind it in and it will hold it self when you put a load on it. Like the cable, you have to leave a full layer on the drum. I can't really see my drum so I painted a black stripe on the rope to let me know when it gets too far out.
Make sure you also replace the fairlead. A fairlead that was previously used with a cable will usually have a lot of burrs and nicks on it that will chew up a rope pretty quickly.
Stew