I am trying to buy some to make fridge magnets with. Anyone know where I can get any? The only ones I have found are those ones you get to put in fish tanks or use for other decorative purposes but they are not always exactly round. I was looking for something thats more of a marble cut in half so the flat side has a blunt corner and is not beveled. Do they exist, does anyone know? Or am I going to have to settle for the decorative kind. I can't find anything through Google searches.