I found this cute reproduction 1930 girl with bubbles fabric, perfect for the job at hand.
Cut out a circle large enough to fold over and glue at the bottom. I used a bowl to make the large circle.
Stuffing batting between the lid and the fabric, glue the fabric down.
It will end up looking like this when it is all glued down. Then cut out a piece of felt smaller than the lid circle.
Insert the top into the mason jar lid, and glue the smaller felt circle in place.
Now I have my very own balloon girl with pins. This has the perfect amount of kitsch and whimsy. I love it!