I second Thorn's topeak handlebar bag. I bought the same on her recommendation and it works great for my S3IS even with the 52mm adapter, uv or polarizer filter, and clip on lens cover (no more of that silly Canon stock lens cover that comes off more than stays on the lens!). I'm even able to get some spare batteries in there and such. I love that it is so easy to remove the bag and carry it around with me at stops.