Can't Buy Stamps at the Supermarket in NY

Last week, I remembered that I needed a book of stamps while I was at the supermarket. So, when I was at the cash register, I asked the lady to add a book of stamps to my bill. She was pretty sure that she heard me wrong, so she asked me to repeat what I'd said. I asked for the book of stamps again, and her response: "Right...this is a grocery store. Try a post office." She was looking at me like I was a complete idiot. I was going to explain the whole California thing, but really nobody cares.