Really BIG pans

Personally I find the paint holding area, even in any commercial studio palette I've seen, to be far too small to suit my tastes.

Half pans are better than nothing for traveling. Full size pans work, but picking up paint from an approximately half inch (2 cm) pan with a large brush can be a problem, especially when that pan sits cheek to jowl with another color. Creatacolor 'bricks' come closest to what I want, each of their 'pans' is the larger than 2 standard pans.

So! I've found that cheap white condiment trays from Freddies do the job pretty good, you betcha, for me. I can fit a brush in them, write the color therein on the edge with a sharpy and, once the paint is dry they stack and store well.

I included the ruler in the picture for scale.

Also I find old cafeteria trays ideal for watercolor work. They'll hold any paper up to 12 by about 14 inches (30 by 40 cm), are great for working wet on wet and clean up with a spray and a wipe.