Add a retractable cargo cover for Prius Three?

Yesterday we bought a Prius Three Touring without first attaching the wimpy fabric cargo cover to see what it looked like. Opinions may differ, of course, but to us, it looks flimsy and useless. It sags so low that it shows the outline of anything in the trunk area, and when you pull anything out, it disconnects itself and has to be reattached. The forward part of the cover rides up on the top of the back seat. It is such a disappointment, coming from an earlier model Prius that had a fine retractable cargo cover that always worked well for us. In fact, we are so disappointed that we probably would have purchased the Four Touring, just to get a decent cargo cover.

I called the dealer's parts shop about buying the "Prius Four Touring Cargo Cover" (for $495!!!) and putting it in our Three Touring. "Oh no," they said. "That's only for the Four Touring!" But it looks to me as though the necessary attachments are present in the Three Touring, too. Has anyone tried this?