What are the alternatives ?
Wrapping paper, white/black plastic (anyone know a name it is called by when asking for it ?), Paint, emergency blankets,
Here is something I recommend on emergency blankets since they wrinlkle, go to an art supply store, buy a large sheet of foam core (available up to 4x

and a can of spray adhesive - then you can spray the board and permanently mount the space blanket on the foam core board. You can use cardboard also.