A "head shop" is where they sell smoking equipment, and usually a variety of smokable herbs. I've no idea if those chinese herb shops sell it, but i doubt it 'cos calea is from mexico! I'm in th UK and have just ordered some from "salvia divinorum supplies". I've read that the name "calea zacatechichi" is a tribal mexican name for "bitter grass". I'm impressed with you, Steff for reasoning with your mother about calea usage! i would never even have considered such a thing, you must have a somewhat cool mum!