Epsom photo quality print paper (or similar) will do the trick, although you'll need a guillotine to cut it to size and with straight edges. I doubt whether demand for a specific size paper would be high enough and most printers won't print to the exact edge of the paper in any case, meaning you'd still need to cut it.
I do hope you're not interested in this for pirate producing purposes
Actually I have a digital video camera and took a friend's wedding video for him. I wanted to put a nice cover on the box, that's all. I'm not sure I could cut the paper very well, so the best idea seemed to be to buy it pre-cut, ie the correct size.
The Playstation 2 mag has a demo dvd free every month, use the case and turn the cover over,it's photo paper & plain white.
Also you could try GAME they give away free game demos on dvd with snapper case.