Anyone need to cover their nipple (giggity)? Sticks to the nipple with a neodymium magnet, takes about 5 pounds to pull it off. These are just a few of the roughly 100 dice I have on hand. Also available are .45 ACP and 10mm cases, which have stronger magnets and are much harder to knock off.
$8 each, 3 for $20. Shipping is $2 for as many as I can cram into a padded envelope (about a dozen before I get concerned about damage).
Note: Not all fill nipples are magnetic. All the Ninjas I've checked have been, but my Guerrilla 48/3k is NOT magnetic, so these won't work. Please attempt to stick a fridge magnet on your fill nipple if you aren't sure.