Underground? Sure. But not impossible to find. Sunnydale even had a magic shop but most of the stuff in it was just...fake, wishy-washy mumbo jumbo stuff. But if you know who to ask then you can get the real ingredients and the spell books and--well, sometimes it's handed down through families. And Sunnydale attracted all kinds of people. Amy's mom had a whole trunk full of witchy paraphenalia. And voodoo doll barbies.