If anyone is interested, a used burlap shade canopy, roughly 10 x 16 feet, with an additional large section. Was used on the playa for a few years. Was well rinsed after the last use, though you can never get all the playa dust out of a thing like that. Fairly good condition.
Seems to block about 50% of the light and is porous enough not to behave like a sail. Tightly packed, it just fits inside a standard plastic tote. I used to suspend it from long (about 10') pieces of rebar that were pounded into the playa. The rebar pieces are available too.
Free to anyone. Hopefully you're in So Cal and can pick it up. Will ship if you pay actual shipping cost.
The Key Man