Aluminum carbon dioxide tanks are available for purchase on Amazon.com, BeverageFactory.com and BeveragElements.com as of 2015. Amazon.com has a wide selection of tanks, including the Guerrilla 12-ounce tank that is suitable for paintball and the Catalina 20-pound tank for keg beer.
BeverageFactory.com has aluminum CO2 tanks with capacities ranging from 5 to 20 pounds. Place orders on the company's website, or visit its store in San Diego, California. As of December 2015, its hours of operation are from 7 a.m. to 6 p.m. PST from Monday to Friday. Its sales department is also open from 10 a.m. to 2 p.m. on Saturday. For aluminum CO2 tanks of larger capacity, BeveragElement.com offers tanks of up to 50 pounds.