MicroMagnets by Zen Magnets – 2.5mm Neo Sphere Rare Earth Magnets (Neoballs) that don't suck
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