I wonder if something like this with the top piece removed (so you can see all the colors) would work. It might not be exact, but it should be similar enough across the board to get the point across and is under $10.
I wonder if something like this with the top piece removed (so you can see all the colors) would work. It might not be exact, but it should be similar enough across the board to get the point across and is under $10.