Chelsea, I got mine from a local gourmet store that had them on a close out.
The best place that I've found on the web is
http://kegman.net/soda_stream.html. Their system is a bit pricey, about
$190 complete, but that way you don't keep on spending 59 to 69 cents per
quart of soda water. You can also go to www.alltheweb.com (my favorite
search engine) and type in soda syphon to see other suppliers.
Good luck and may your life be filled with bubbles!