I was stumped on how to get them to stop rolling around in my car because I figure they are perfect for water storage in the car (also in a pinch the water can be sanitized in the sun for several hours). I then found a place that sells em and they are less than 2 dollars each on this guy's ebay store.
http://cgi.ebay.com/Coca-Cola-Pepsi-...item230a36cc28