You can occasionally find the purple wallpaper on sites like Spoonflower and such, but it usually gets taken down after a bit. Most people just paint the wall purple and then use stencils to do the face pattern.
You can still buy the foyer wallpaper though (which I kind of like better, also it's a little more low key. Somebody would have to KNOW the mansion to get it) from the original manufacturer.
Lily Floral Wallpaper | Bradbury Victorian Style Home Wallpapers