On our recent trip to Fredericksburg, I purchased a tiny mint tin because it reminded me of a friend and co-worker who portrayed Rosie the Riveter in historic presentations. Teresa's aunt had actually been a riveter during World War II, and much of the material was based on her memories. And now the tin has been turned into a wee paint box. I tested my color choices on this page.
A silicon mini ice cube tray from Amazon was cut up to fit the tin with 9 spaces for tube paint to be squeezed into. While I was at it, I cut another to fit the Texas mint tin I purchased when we were planning to move to Texas. Formerly it held 6 half-pans of paint; now it can hold 12 colors plus a bit of a natural sponge.
The bare minimum of tools to take along with me . . . one of these tiny tins, a fountain pen, a waterbrush, and my journal.