It was this site
But, I did a search for Bettas and only one book came up (for $1.69 I think). I did a search for betta maurus to include the authors last name and got the book I was looking for. So their search is a little whacky but if you know the title or author you might have better luck.
I looked on Amazon and found the book through them, shipped by that Owls Books. And it was $4.99 plus shipping. Having sold books on Amazon myself at one point I knew that Amazon gets a cut so the sellers will have higher prices when selling through Amazon. So I went straight to the source instead. Got lucky:)