Amazon.com and eBay.com both carry 5-gallon water bottles. Many brick-and-mortar stores such as Wal-Mart and Home Depot carry the bottles in their stores and online.
As of 2015, an empty 5-gallon water bottle costs just under $19 on Amazon.com. It includes free shipping.
On EBay.com, an empty 5-gallon water bottle costs between $16 and $25 depending on whether or not it has a spigot. Ebay.com also offers free shipping.
As of 2015, the price of a 5-gallon water bottle at Wal-Mart is $17. At Home Depot it is approximately $14. The price includes the water, not just an empty bottle.