I found these in the button section at Joann's. They have packages of different shapes labelled Favorite Findings. These usually go on sale once a month and you can pick a pack for around $1.15. I believe there was enough to make 12 or 13 pairs.
Glue, earring post. Super simple! With all of the birthday parties kids get invited to this would make a great girl gift!
Check out all of the places I party here!