I carry bear spray, although I have never had to use it I have encountered a few black bears with no issues. Some mountain parks actually require you to carry it on their trails.
I cut the top off a water bottle and a standard bear spray can fits snugly in it. I carry it in a the bottle cage on my frame. It stays secure, but pulls out fast when you need it without undoing any Velcro. You don't have to make your own as you can buy one at MEC here:
https://www.mec.ca/en/product/5038-9...-Spray-Holster