I want to have boards for my boys and myself to do wet on wet painting as well as to use for drawing when we're outside etc. I was hoping to find a huge clipboard or something on Amazon (I'm in Alaska so their free shipping is a huge enticement) but didn't.
We ordered ours from Paper Scissors Stone, which sells mail order waldorf supplies. I think a local family makes those and their chalkboards BTW. We've used them constantly for YEARS for both drawing and painting.
They are very lightweight (wood composite?) with an extremely smooth laminate surface that wipes clean.
I use a masonite gesso board that you can get at any hobby/craft store for a few bucks for my watercolor painting. Tape down the corners using artist tape, or masking tape (masking tape is not suitable for fine art painting as it has acid in it and will leave a residue) but for learning, student stuff you can use it. I use it for my paintings until I can find some artist tape.