Empty palettes from Schminke and Holbein. I filled them with paint.
The next larger palettes hold much more paint and have large mixing areas. These I use when I'm carrying larger papers and when I'm on a painting excursion. I can get quite a large wash done with these and they still are neither too large nor too heavy to be comfortable to carry.
These are just a few examples of palettes suitable for travel. You will be able to "see" possibilities for all sorts of solutions once you really begin to look.