Where can you buy a concept art book of Golden Sun the Viedo Game

I don't think you can buy concept/art books from any of the Golden Sun series because the entire book would be filled more with character sprites and pixelated backgrounds, it wouldn't be enough pages for an official art book. You can probably buy the strategy guide for some images (although it wouldn't really pack that much with conceptual art and designs) or you could find some decent concept art of backgrounds and character lying around in the related link.