Homer what I have done for an emergency shelter is to purchase a good quality tent footprint. It is very quiet, lightweight, and packs into a very small space. Another plus is it has 6 grommet spots already in place. You can just purchase the footprint that you think would cover you. I believe mine is 10' x 8'. I always have it in my pack just in case.
I use a section of thermal tarp. Not sure where to buy them, we have them at work for frost blanketing for excavation. It's a very thin, lightweight, waterproof tarp and appears to have some sort of mylar woven in. Usually some get partially burned by frost removal equipment and I can cut out the good sections and throw the rest away. I have one that is 6X8 and another that is 10x12. I keep the larger one in a vehicle. The smaller folds into a pack taking up only slightly more space than a space blanket. I have used it for winter camping in sub-zero weather and as an emergency rain-fly when our proper rain fly was carried off by some gusty winds. The material is ripstop. Just use duct tape and a sharp knife to make your own grommet/tie down holes.