Hey there. In watercolor it is very common to fill travel pallettes with liquid watercolor tubes--just squirt it in and let them dry till they are solid. A good quality yet affordable set would be something like Winsor and Newton Cotman. They aren't "artist grade" so some of the colors will be made from a few different "hue" pigments, but they are decent quality in my experience. Here is a set of 20 tubes on amazon, though they have sets of different sizes and with different colors. It all depends on what you want. One 8ml tube should be good for 5 or 6 half-pans (which are about 1.5ml in volume), so one of those sets should be good for 5 or 6 pallettes.