Hi Angela! You can find them at most toy stores, some floral stores, and at the Amazon Affiliate links provided in the list of acorn marble ornament craft supplies.

Hi Sasha,

So sorry about the delayed response. We have linked to all the supplies that we used in the supplies section above. We used a combination of standard playing marbles you can find in the toy store and round translucent marbles commonly found in the floral department. Because acorn caps come in all shapes and sizes its hard to tell you which will work for you. Some acorn caps are too tiny for marbles, while others are too big, and a few are just large enough to fit a shooter marble. Use what works!