jayco pop-up camper lift cables
The first place I would try is Jayco. Most manufacturers are willing to help even if they no longer stock the parts themselves.
If the cables are badly worn, I would also look into replacing the pulleys they go around. You will have the cables out to change them anyway, so why not assure maximum life from the new cables?
I worked on one of these systems years ago, and it wasn't too bad to figure out. The key is getting parts that fit and not dropping the top on yourself while the cables are off. (The one I worked on had to have the top part way up to get at the cables so I blocked it in place before removing any parts.)
If you are unsure at all about how things go together, get out your video camera and record the disassembly so you have a visual and audio record of how it looked together and how it came apart.
