Here is a video of a technique for making plastic tarps. Would work for Polycryo window screens, or, as here with polythene sheets (painter drop cloths). Good tensile strength,but can easily be punctured. Easily repaired with duct tape.https://www.youtube.com/watch?v=FgCUc_aUnb0
Total material cost as low as $10 With a patio door window insulating screen at about $8, you can make a pretty good "tarp" weighing 100-120 grams.