These are the paint palettes I use in the studio. I've used them for years now and been very impressed with them. Brilliant, nifty and highly recommended.
They are made of substantial, slightly flexible plastic and can be washed and re-used again and again. I paint with artists acrylics and often have four palettes on the go; when I have finished I stand them in the sink with a bit of water on them and after a while most of the paint just slides off. Any remaining paint can be taken off with a nylon scourer and water.
About 8 x 12 cm with rounded corners and rounded edge moulding too; no sharp corners. Great for children to use, but not deep wells for giant paint puddles!