For polycro, I bought a 62"x210" window film kit at Home Depot for $6.49. A 31"x96" section is 1.4oz. You can get 4 sheets that size from the kit, plus a little more. You can wrap your tent stakes in a small section. I use that for kneeling to get in my shelter, like a doormat.
What I bought is a Frost King Extra Large Window Insulation Kit, part number V95, bar code 0 77578 01812 6. You get a handy-dandy roll of super sticky double-sided tape with it.