The two options I've found are the RayShade (approx $25 for a double) and the Protect-a-Bub (approx $50).
RayShades come in navy or black, attach with velcro, have pockets for storage, and are a stretchy material with a slight shiny sheen.
Protect-a-Bubs come in black (or navy I think) and some have contrasting color piping on the edges. They attach with ties and are a matte material with mesh-like openings. Of the two, this fabric seems like it will breathe more and be cooler, but at twice the price, it may not be enough of a difference to be worthwhile.