20pcs 12mm x 3mm (1/2" x 1/8") Disc Magnets – Magnet Baron
Amazon.com: WOTOY 140 Pieces 3mm D x 3mm H DIY Fridge Magnet Multi-Use for Door Whiteboard Map Screen Bulletin Boards Refrigerator Magnets : Everything Else
10mm x 3mm N52 neodymium magnets round discs 3/8in x 1/8in
3 mm x 1 mm DIY Office Magenets for Fridge,Whiteboard,Craft,Project,Art - 300PIECES: Amazon.com: Industrial & Scientific