Are you talking about a disk that has little massage fingers on one side and low bumps on the other. It acts like an exercise ball without the rolling that you set on a chair? If that is what you are looking at I originally spent big money on one from an OT store and then I found one at Walmart in the sports goods area.

http://www.walmart.com/ip/Amber-Sporting-Goods-...

I got my son's disk at Ross Dress for Less for about $10. Exercise balls too for a fraction of the cost- they are the same as the expensive therapy balls.
The dollar section at Target also has great fidget toys, I see the same product for $5 each on line- I load up every couple of months.

Awesome! Thanks!