Oh, man...I'd forgotten about those. Used to see them everywhere on just about any make or model available. I guess the new wore off the chandelier, huh?
Every since I bought my first Elantra, I've cruised the various websites. I can't remember ever seeing one. Might be an interesting look. They were sort of the predecessors of tinted windows, weren't they? To keep the sun off the rear window and reduce glare? Plus the obvious cosmetic appeal?
Not sure if they were all like this, but the one I had on my old Z had some nice features: you could release it at the aft end (it was hinged near the front) and lift the entire assembly for cleaning the outside of the rear window. It somehow clipped onto the rear window trim (I installed it but it was 1984 or so, the Miller Light has washed away most of those memories....) in such a manner that it was easily removed if you needed to.
Altogether it was a very nice accessory, not very aerodynamic though. I would consider putting one on the Elantra if someone still made them.