I know I say this often, but I absolutely love my pochade. It's great for travelling, painting away from home and even painting at home as I can move around from living room to kitchen to patio. I always have it ready with primary colours (ultramarine blue, hansa yellow medium, and napthol red) along with titanium white and then I like to throw a couple of fun colours in the box - like dioxazine purple and alizarin crimson. Along with paint, I always have a spray bottle ready to wet my paints or canvas and a stay-wet palette. I also carry a set of inexpensive brushes, a rag and brush washer, and when travelling I carry a pen and small sketchbook either in the box or in my purse.
If you're interested in my pochade, it is the 6x8 Thumbox by Guerilla Painter. It's no longer made as deep as mine so you may have to invest in a smaller brush washer (or collapsible one) but that also means it would be a bit lighter, too. It is also available smaller (5x7) and larger (up to 13x17). The great thing is that there are extra pieces and replacement parts available and I like that I can use it on a tabletop (mine has rubber feet), attached to a tripod (with a tripod mount), on my lap or in my arms while standing (it has a great thumb hole at the bottom. I use mine to paint 4x4 to 8x10 (vertically), though on occasion I do prop a larger canvas on it as well. The one similar to mine can be viewed here.
I love these Royal & Langnickel brushes and even use them when I work larger. Because I'm quite hard on bristles, I am glad I can replace them inexpensively but they do last quite awhile. I like the fact that they are smooth and hold a lot of water for smaller brushes. Also, because the handles are plastic, the ferrules never loosen like they do on wooden brushes as they expand and contract. And they fit into my pochade perfectly. They are available at many craft suppliers (including Michael's).