need a groundsheet

[NettleTea]

Looking for a groundsheet which is 4m square. Ive seen lots listed, they are often the make of a tent, so when I look at the details they dont give me the dimensions. any tips or ideas?

If you want a free standing one, have you considered a pond liner? Far more hard-wearing than that Chinese plastic woven carrier bag stuff they're usually made of! And you can buy the size you need.