You can get it from Cattv.com or on ebay, they have an authorized distributor who lists them on ebay and they are actually a few bucks cheaper that way.
I know this because when I saw someone selling multiple copies for cheap, I contacted Video Catnip to let them know someone was doing that. They got back to me and let me know it was ok, they knew the person who was selling them!
I was afraid they were bootleg or something, but they are legit.
My cats love the DVD, by the way! Their cousins in CA currently are borrowing it and love it too!
Molly sometimes watches TV. Once we were watching a show about different pets, and I heard a loud THUNK. Molly got up from the floor shaking her head a little, she tried to attack the bird that was on the TV. Silly girl.