Amazon.com : 8" Gray Foam Ball (Often Used to Make a DIY Mic Isolator) : Playground Balls : Toys & Games
Amazon.com: BUHOET 7-Inch Uncoated High Density Foam Ball-for Over 3 Years Old Kids Foam Sports Balls-Soft and Bouncy, Lightweight and Easy to Grasp Foam Silent Balls are Safe for Younger Children(Rose Purple) :
Rainbow Low-Bounce/High-Density Uncoated-Foam Ball - Gopher Sport
Champion Sports Uncoated Regular Density Foam Ball, 8.5", Yellow, Pack Of 2 : Target
Custom High Density Vibrating Foam Ball
High Density Foam Ball, Uncoated, 8" - Walmart.com