There is this company I know of - Killing Fields Terrain (I believe from US). They make amazing mats. I wanted to buy one of theirs. Sadly, due to the supply shortages they ceased all shipments, at least temporally. So, being out of satisfying options I had to have a go myself. There is the saying “need is the mother of invention”.
One thing is that I made the size exactly for my needs: 150cm x 200cm I think it’s 5’x6,5’ Their largest is 5’x7’ which is a foot shorter than you need so you would have to make either a special order or make it yourself.
I also was looking for some other grass mat products and I found few decorative mats but they wouldn’t be any good as a gaming mat. I ordered one small sample of such product but although it looked alright, it was very impractical.