Back in the day I knitted something similar for myself, though I don't recall if I'd seen the original product.

In fact earlier this year I bought a new kindle and knitted a little "sock" for it:

https://www.instagram.com/p/DGTsi5SM9YM/

Just knit a rectangle, and sew two edges together to make a flat "sock" or "envelope". I was done in a couple of hours, but I guess I'm used to knitting in front of the TV.