I’ve always been a little confused by the mystique attached to painting outdoors. If you paint nature from observation, of course you have to go outside to do it, unless you have a very good window, but is it more romantic if we do it in French (en plein air)?
In any case, often people new to it overload themselves with stuff, or could use some help about useful things to bring along. My keywords for painting outdoors are: cheap, lightweight, and time-saving. Hopefully some of my ideas will lead you to come up with solutions of your own. I made a brush holder (or conteneur des pinceaux :)) from a Moravian cookie container, string, and lots of tape. It hangs from the wing nut on the side of my French easel and ties to the leg. I also put some self-adhesive Velcro (invented by a French person, not to mention the easel) on it and on the leg to make it a little more steady. It’s been working well for years, cost almost nothing, and I really enjoyed the Moravian cookies. The elegant paper towel device is a binder clip from Staples; I carry of lot of these in various sizes because they are so useful. Today we made a makeshift hat for my painting friend who had forgotten hers by using binder clips to clip a piece of cardboard to her hair.