I had almost forgotten I had this. It's a special charity book issued by Waterstone's, I think back in 2009. It contains a number of VERY short stories by various authors, including J.K.Rowling and Neil Gaiman, all written in the authors' handwriting, in what approximates a post card size and card stock. The J.K.Rowling story is a "prequel" to the HP series, featuring James Potter (Harry's father) and Sirius Black, back when they were teenagers. I'd estimate its length at about 1000 words.

Front:



Back:



I don't know if it's still available.

John