I just took a quick vacation with my wife, and found a handy "bowl" for shaving: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It's actually a camping cup made by Sea To Summit. It's a silicon rubber kind of material, and is made in a set of concentric rings that allow it to be squished into a flat disk for storage. Also, I quickly discovered you don't have to completely open it. I would usually push it about half-way open to make it a perfect depth for my brush. As a bonus, when you do this, you get some ridges in the bottom of the cup for working lather. They make a couple different sizes, also. But this one seemed about right for me. It won't replace a nice shaving bowl at home, but it is good for travel, and practically indestructible.