Decaying tonneau cover (cargo security cover)

My wife and I have a 2010 Prius with the OEM tonneau cover (“windowshade” cargo security cover) which is falling apart due to age and daily use. Never mind the dirt and gray stains; the real problem developing is that the vinyl cloth material is fraying at the edges and has separated, exposing the cardboard reinforcement stiffener at the rear edge.

We park on-street in a dense urban environment, and consider the security cover to be essential in discouraging thieves (we don’t leave valuables in the car overnight, but can’t avoid this occasionally while running errands).

We don’t want to use duct tape or some other adhesive tape, because of the well-known tendency of the adhesive to react with the vinyl plasticizers to produce a sticky, messy “goo”.

We have looked for a replacement for the flexible cover or the entire assembly, but haven’t found much other than occasional used ones of unknown quality and high prices. Any suggestions on how to make a durable repair, or to find a workable replacement?