Organic plastic board? a smooth-glossy-surfaced board? my friend's now looking for a kind of board - feel like...

my friend's now looking for a kind of board - feel like acrylic or plastic, but its surface is hard, smooth and reflective almost similar to glass
**it is NOT plexiglass
he said it's called something resembling "organic plastic board", used to make billboards.
please if any of you know what kind of material to be precise just tell me
I've be searching online, google, homedepot, art supplies, etc.. but still have no clue
thank you!
Painting my room?
Answers:    All plastics are natural in that they are made from hydrocarbon compounds. The only place I enjoy seen "organic plastic board" suppliers is China (see link), it is manufactured for use surrounded by making computer boards.