My first ball was purchased in a New Age store. lots of these around, especially near college towns, it seems. however, the 2nd ball I purchased as a gift for my mother and found it in a mall of places! it's very small, but i liked that, as my mother is elderly now and has arthritis, so I did not want anything too big and heavy for her. She is beginning (since Christmas) to have some results, (though she is a natural!), so it seems like it was a good buy.
I heard (here on AT?) that a smaller ball is actually easier to read from! I never would have thought, and now, I wish I would have purchased two of the small ones at Christmas. It was a kiask, and now the guy is not there---guess he is only around at Christmas. My loss.
But, see if you can locate a New Age store near by you.
Good luck!