............. tried to use the manual cables only to find out previous owner broke both cables! Does anyone know who still makes these cables?
Are you sure that your cables are broken or are they just pulled free of the bulkhead wall. I’ve seen several R’s where someone has tried to use the roof tonneau cover cables and they pulled them free of the cable mounts in the wall. To use the cables, you insert the roof tool into the loop of the correct cable and pull toward front of the truck AND
slightly upward (upward at 45 degrees as per owners manual). The cables are held into slots in the bulkhead wall and secured there by a plastic strip adhered to the wall. If you pull downward, you can pull the strip free and the cables will release from their slots. Also, you need to pull slowly and steadily as you are pulling against hydraulic fluid in the latch cylinders, and remember you must release each side (driver and passenger side) separately. Cables marked with GREEN ferrule to open tonneau cover, cables with RED ferrule to latch tonneau cover closed.
The plastic strips that secure the roof cables are usually hidden behind the bulkhead carpet, but in the picture attached below you can see the cables and retainer strip.