Here is an example. While I have used one as a ground cloth for decades and it has held up for me, I do not know the longevity of this specific brand nor do I know the reputation of the seller.
The mylar tarp is definitely a huge upgrade. I have one that's big enough to wrap up like a human burrito. Comparable in size to a queen size blanket with reinforced edges and numerous metal grommet holes.
It's an absolute must have in any area that gets any snow or ice. I've been stranded in my car for a few hours and it's always better to have boots, snowsuit and quality tarp on hand.
Here is the same tarp another poster linked, 60" x 82". I have one almost identical.
I can’t find the exact product link but I use something similar to this: Insulated Thermal Reflective Tarp -https://www.amazon.com/dp/B01H6NC8XU/ref=cm_sw_r_cp_api_i_BDBZCbVBCJCA4
It’s as sturdy as a tarp and has those holes so I can put them on the top of my tent, but leave a layer of air between them and my tent (v. important) by staking them in the ground.
Remember, making that pocket of air to create the shade is what turns your tent from a cool retreat into a baked potato