Another option is a marine fabric, such as
"Stamoid Double Coated Canvas",
found here.
Quote:
| Stamoid is guaranteed to withstand climates that range from the hottest Florida summers, to the coldest Great Lakes winters, to the wettest Northwestern months. Stamoid exterior marine fabrics have provided long lasting, durable quality on boats of all sizes world wide for decades. |
It comes in 80" widths, for $64/yd. So, you'd be looking at $2-300 for something like this.
It comes in a variety of colors:
WHITE
SNOW WHITE
PEARL GREY (very likely way too dark, unless you have lumens o' plenty...which would be surprising on that giant screen)