The Chapeau in Magic Kingdom is located on Main Street near The Confectionery. It is the place to purchase your Mickey Ears. They carry a wide assortment of ears and you can have them monogramed right there in the store.
Make sure pick up the phone in The Chapeau. It is located up the ramp near where they monogram the ears.
Learn more about souvenirs in the Walt Disney World parks plus Destinations in Florida can help you choose your souvenir purchases on your next Walt Disney World vacation.