This guy has tested the ghosting properties of a bunch of different types of plastic, and he made himself a pretty good ghosting-free whiteboard that photographs well out of Polypropylene. He says marks can stay on for weeks and still erase completely.

I've done a bit more googling and I found this link. So it looks like melamine-coated plywood is available at hardware stores. It's considerably more expensive than the first link, but still cheap. And at least the minimum order isn't 100 cubic meters! What you might want to do is bring your dry-erase markers to a warehouse hardware store and test them on the melamine and whatever other materials look promising.

Also I forgot to include this in my last post: I used liquid chalk on glass back when I worked at a restaurant. Smiggle is the best brand, and very erasable. Some of the others are hard to erase without window cleaning fluid. I'm not sure if they sell it in the US though.