I came across Laure Ferlita's blog which led me to her demonstration video on the "No Excuses Sketch Kit". This kit is so small, so compact, that there is absolutely no excuse why someone who wants to sketch on-the-go could complain of lack of materials on hand. Your watercolor palette is simply patches of pigment scribbled in from watercolor pencils onto a folded piece of watercolor paper. To use the pigment, simply apply the tip of a waterbrush to the patch and get some color and paint!
Years ago I found a Derwent 36-color watercolor pencil set for a good price ($20 I think) at Costco and picked it up--and consequently hardly ever used it. Now Laure has inspired me to make a good use of it! So I gave it a try, and did a little ACEO-sized painting (on Yupo paper) with it:
Now this is a kit I can actually put into my small purse! Thanks, Laure!