Where can I find an oversized golf ball that is used for putting practice that measures about 3" in diameter?

I recently saw it on the golf channel. The idea behind the ball was that if you putted with this ball for a few minutes than you switched back to a regular size ball, the ball would look like a marble rolling into the cup!Where can I find an oversized golf ball that is used for putting practice that measures about 3" in diameter?I have never seen this before, but if anyone has it Golfsmith.com would be the place to go.Where can I find an oversized golf ball that is used for putting practice that measures about 3" in diameter?Easily Golfsmith, but they are about 1-3 dollars more than regular size.Where can I find an oversized golf ball that is used for putting practice that measures about 3" in diameter?You can accomplish this with a common tennis ball.