Sta-wet & similar palettes
I have been using a Sta-wet palette for my Ceracolors (water soluble wax paint) plein air for a few months now. Haven't tried it for acrylics, etc., but have to say so far that I am astounded at how well it's been working for me!
I have had none of the mold issue that others talk about and one piece of the Sta-wet palette paper has been lasting for months. In fact, the paints on my palette have now been moist and open when sealed for about 6-8 weeks!
Just bought a smaller Guerilla Painter version, which I understand is made by Sta-Wet, though it did not come with sponge or paper (I can adapt that from Sta-Wet stuff or household items.) This also appears to seal well, but I haven't tested it in the field as yet.
Was expecting to have problems with the paper, but in fact it is strong enough to not tear or buckle when wet and when covered in paint. I'm told it can be rinsed if still moist and used for looooonnnng periods.