You can buy corflute in many different colors and thicknesses. Only issue might be how you'd glue the seams tidily together.
You could use thin foamboard (available from bunnings i think, has a paper layer) to make the shape, then cover the inside with a few layers of fibreglass tissue and resin (could even throw some black pigment into this)
I could post you some fiberglass tissue if you went this route. I have lots here from an ali express order.