I have had some issues with my old travel palette (Cathy will recognize this - it's an old Winsor & Newton travel palette that holds full pans. She has one that's identical) I took out the pans and use tube watercolor in the small wells. Below is a photo of my current portable sketch set. The W&N palette, a collapsable water cup, two Utrecht travel brushes, a 1-inch flat squirrel hair brush, a small flat synthetic and a rigger. This is the set I use to paint 95% of the Urban Sketching paintings that I do. I also have a larger travel palette that's really nice and has a lid that seals - but it's too large to carry easily sometimes.
I have to include a disclaimer here - I am not advocating the use of a tobacco product, it just happens that the little tins that Camel Snus comes in (snuff in pouches) are perfect for setting up a mini portable palette. You could buy a tin of Snus for about $6 and throw out the snus, ask a friend who uses it for one of their old tins (that is what I did) or look on eBay as I've seen people selling small bunches of empty tins there. Here is a photo of the tin with my glasses close by for size comparison.
As you can see, it's very small - which is something I was looking for. The other thing I was looking for was that I wanted something that had a watertight lid.
If you look closely at the inside of the lid, you'll see a small rubber/foam seal that circles the edge.
It holds 8 half pans perfectly! I painted the inside of the lid with an off-white spray enamel to make it easier to judge colors. (A tip I took from one of Cathy's posts on setting up a portable palette - thanks, Cathy) I used masking tape to cover the foam seal and the outer portion of the lid. I used small dabs of RTV Silicone on the bottom of each half pan to hold them securely in place. As you can see - it's small enough to fit nicely in the palm of your hand, or your pocket. It's a little bit of a challenge to open, but not too difficult. I'll let you know how it goes after I've tried it out a few times.
I'm also in the process of setting up a slightly larger palette in a waterproof cell phone case. (Photo below) It was $5.97 at Walmart. Once I get it completed, I'll post photos and info on how I set it up.
I hope some of you find this useful - I'm looking forward to putting this little fella through the paces.