I have a fanny pack I throw anything extra I think I might need. At least it's good for a bottle of water. I seldom carry anything extra in the tool department. Pliers would be a good thing, though, or a Leatherman. I used to carry the stuff under the webbing on the rear of my seat, but I've lost a few things out of that, so I went back to the fanny pack. Those served me well in my enduro riding days, and it still works fine!
Bare