I've read that pumpkin juice is a favorite drink of wizards and witches.  It's the same size as a real bottle cap, with a 3-D wiggly edge, and the back of the cap is even recessed a bit.

The word "Pumpkin" is custom-lettered for a peppy mid-century soda pop look. The pin uses orange hard enamel, in gold or silver metal. 28mm wide.

Designed by Rather Keen