So where do we get additional game pieces.
Mike,
I spoke with Terri Kroll yesterday at kickoff specifically about this issue and she said she received a large volume from http://www.fivebelow.com for $5/pc.
I did find some similiar if not the same, large, 8-1/2 tennis balls on amazon but for around $12/pc.
Some Toys-R-Us stores carry them, too; there are other on-line sources, as well, but Five-Below could deliver them fastest because they had a large inventory.