3" x 5" Clear Magnetic Label Holders - Top Loading Business Card Holders, 50 Pack - Perfect for Office Organization, Retail Displays & Fridge Magnets

while not a sophisticated product, this magnetic holder can use standard index cards and magnets are powerful enough to work. the magnet is not in a separate slot holder so you have to fumble around a bit to position the magnet behind the index card. not rocket science not deal with.