How can I find out where on earth to buy a wallpaper to clash a piece I already enjoy? ...

Kilz Over Stain & Varnish To Avoid Sanding?
Answers:    I took mine to Sherwin Williams....other places like Home Depot or Lowes might know how to do it too.........
Decor/theme Idea for New bedroom !?
Find writing somewhere on the existing wallpaper and google it. Or take a picture of it and stir to various home advancement stores and see if they can match it.