Reddit mentions of Frost King Clear Shrink Indoor Patio Door Insulator Kit 84 in. W x 110 in. L

Given that this is an UL forum, we might mention that in addition to costing a fraction of the manufacturer footprint, a footprint made of polycryo or tyvek will weigh a fraction as much. You can buy a polycryo sheet for less than $10 that will give enough material for two footprints at less than 2oz each. That compares to the Passage 2 manufacturer footprint at $30 and 8.2 oz. ( https://www.amazon.com/Shrink-Window-Insulation-Picture-Windows/dp/B00PCHY4VM ) People in this forum are generally in favor of paying more money to get less weight, not paying more to have more weight. ;)

These things are not rocket science. All you "need" (and you probably don't really need that) is a rectangular sheet that you place under your tent. Done. People have gone entire thru-hikes (i.e., over 100 nights) with a single polycryo groundsheet. Why would you bother using something heavier? Grommets and use of rainfly on its own is potentially a reason, but (1) few people ever do that, the people purchasing a tent are not usually the people who also like sleeping without an inner-tent to protect them from bugs and critters, and (2) a polycryo sheet is so cheap you might as well have one for the vast majority of your trips when you're using both inner-tent and rainfly. Or, just go without a groundsheet at all; the floors in most tents are strong enough by themselves -- unless you're often camping on sharp rocks or needled plants -- and even then repairing a small poke through is not a big deal.