If I have to carry something that I can't put in a jersey pocket or a tool bag, I would rather have it in something strapped to a rear rack. Of course, you have to have a rear rack to make that work. Some of my older bikes only have cage bosses on the DT. I think they started putting them on the ST around 1985 or 1986. Anyway for the rides that might need more than one in the cage and some in a jersey pocket, I have one of these that can add some more capacity.

https://www.wolftoothcomponents.com/...cessory-device