Adhesive Swivel Casters 8 Pcs Cute Mini Self Adhesive Caster Plastic Wheel Caster Ball Caster Small Slide Box Moving Carton Accessories for DIY Box Toy Car Cloth Bin Storage Container Small Furniture :
10pcs Miniature 8mm Robot Bearing Steel Ball Roller Ksm-8 Swivel Round Ball Caster Drop In Universal Small Ball Transfer Unit - Furniture Casters - AliExpress
Pololu Ball Caster with 1/2″ Plastic Ball
Ball Caster - 3/4 Metal Ball : ID 1200 : $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits