Originally Posted by potfish

Try contacting any of these companies to see if they can help. They are mountain bike rental places, but if they can't help they can put you on the right track.

http://www.laclusaz.com/ete-summer10...ons-de-vtt.htm

Alternatively one online place is here: (no experience of this company, but tells you what you want in French if nothing else)
http://www.alibabike.com/721-gonflag...cartouches-co2