Cheers to seltzer water!

Zero calories and good for my health? It got my attention! :D
After buying my first bottle in Wal-Mart, good fortune caught me and Publix had their brand on sale for .50 USD a bottle! :] (But one get one free at .99 USD per bottle).

I bought six bottles. One was a Club Soda, which is my favorite now and the rest were lime or raspberry flavored (a.k.a. they had a lime or raspberry taste going down and an odd aftertaste... not bad, just odd - you know?)

After some Googling, I realized that you could make carbonated water at home with machines like these:

http://www.amazon.com/Sodastream-Fountain-Soda-Maker-Starter/dp/B001KYT6CS

http://www.williams-sonoma.com/products/sodastream-penguin-water-carbonator/

These machines cost about 100-200 USD. The main thing that bothers me is that the product descriptions  usually say that a "carbonator" is included that makes about 60L. After that one runs out, where do I buy more? Do I have to buy a specific kind?

If you have answers to these questions or any general statements please comment below :3

P.S. This seems like a great website for water-carbonating products: http://www.sodastreamusa.com/default.aspx