Actually, you need Gaffer's Tape, which is about 30 bucks a roll, but well worth it. No sticky residue on your camera. I keep plenty of small strips on my lens hoods and the bottom of the camera for when I need it.
That said, I've been using Canon 1-series cameras for seven years (the mark I and mark II versions). These have built-in interlocks to prevent this sort of accidental change. For some reason, the interlocks were widely criticized by photographers, and they've been eliminated on the Mark III series cameras. BAD IDEA! I tested a 1Ds Mark III this summer, and managed to accidentally change the file type (from RAW to Small JPEG!), the ISO, the shooting mode, and various other settings while out shooting under normal working conditions. It's highly, highly annoying.