These buttons are now available at Guest Relations and any indoor merchandise location.
If you're celebrating a special event at Walt Disney World, make sure you stop by ‘City Hall’ in the Magic Kingdom, or ‘Guest Services' in EPCOT, Disney Hollywood Studios or Disney's Animal Kingdom. You can ask for a complimentary button to wear during your visit. (They'll write your name on the Birthday Buttons.)
These always generate special attention from the Cast Members as well as other guests. The buttons are 3 inches round.