When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am in Australia and the type of shade you want is available here called "snap shades". They are available from general auto accessory shops as well as on ebay.
You could try using magnetic or suction car shades. They cover the rear windows and the back area without needing to stretch them. Make sure they have UV protection. ShadeSox and Enovoe make good ones.