This seems like an ideal light tarp for not too much money:
http://www.msrgear.com/tents/ewing.asp
44 ft^2, 6 oz.
My only concern is that the curves seem to be rather exaggerated so that when pitched as shown with a ridge and edges to the ground, the ridge is high and may not provide as much protection as a flat tarp or catenary tarp. The windbreak configuration looks good though.

