After my first rural 'chased by a dog' encounter, I found the Halt pepper spray newbert mentioned and a plastic handle bar clip that looks like 2 letter Cs attached at 90° angles. One C snaps on your handle bar, the other holds the pepper spray can. Quick & easy to remove for dog use & easy to switch bike to bike. I can seem to find the clip anywhere, but perhaps an open (c-shaped, flexible material) flashlight mount would work? Check the fit/diameter, sorry can't post a pic yet.