500pcs Tiny Mini Magnetic Magnets 1x0.5 mm Small Round Micro Ndfeb Imanes Diameter 1mm x 0.5mm Neodymium Disc Sensor Mini 1*0.5 - AliExpress Home Improvement
MicroMagnets by Zen Magnets – 2.5mm Neo Sphere Rare Earth Magnets (Neoballs) that don't suck
MicroMagnets-Set of 1728 - Walmart.com
Amazon.com: 200Pcs Small Magnets, 3x2 mm Mini Tiny Round Magnets, Micro Magnets for Crafts, Miniatures, Refrigerator, Whiteboard : Home & Kitchen