I have a helmet mirror, and it works well for me. Some swear by the ones that attach to eyeglasses or sunglasses, I don't see why a decent one wouldn't work well. I don't use it instead of looking back, but it gives you more time to check things out and spot trouble.

My trunk bag has a carry handle on the front of it, so it's like right behind my seat. My pepper spray has a belt clip, which works fine on the trunk bag handle. It's an easy reach to get to it. I pulled it this past weekend when a dog seemed intent on going after my daughter, but he was just a runner so I didn't use it. Was the first time I had pulled it in a "real world" situation, and it was fast and easy. Wasn't hard to get it back in place either.