I have two of the three models of the Topeak handlebar bags. The small bag for commuting and short trips. The medium size for touring with my camera. It's a great camera bag for travel. I found the large one was too large for me.
http://www.topeak.com/products/Bags/...deHandlebarBag
I bought 5 of the mounts: one of each of four of my bikes plus a spare. It uses a wire to hold the mount in place. I take the extra mount with me when I go on vacation and rent bikes. I've easily been able to mount, remove and remount it on different rental bikes.
I highly recommend these Topeak bags.