As some of you may know, it can be difficult to locate replacement o-rings for Canon waterproof cases. Canon's recommendation is to replace the o-ring every year, which seems like a good idea. A very old SB post (from 2003!) listed a Canon phone number in the U.S. that you could call to obtain new O-rings. Amazingly, today I called the number listed in the old post, 732-521-7007, and it actually still worked! The number appears to be aimed at professional Canon repair people, but (as the old SB post stated), simply ask for the "parts department". I was switched to a very helpful American (not a call center) who easily filled my order for spare o-rings. The cost is about $16/o-ring. I highly recommend this if you are looking for replacement o-rings.