Amazon.com: Mega Crafts White Poly Craft Foam 12 Inch Ball, Durable, Solid Polystyrene Balls for Arts & Crafts, Ornaments, School Projects, Knitting & Party Favors, Great for Kids, Teachers & Artists :
Amazon.com: Craft Foam Balls - 1-Pack Large Smooth and Round Polystyrene Foam Balls for Art and Craft Use - Makes DIY Ornaments, Wedding Decor, Science Modeling, School Projects - White (6 inch) :