Don't even think I forgot this topic!
But I was so busy (work).
Finally I found the best material, it is called "raffia de polietileno", it's white, has a woven appearance an some people use it in making windcar's SAILS!
And it's very inexpensive
Good enough for me, problem was solved
What a curious thing, in my research i found a material called "trapaulin" a trade mark from Uruguay for a plastic tarp. Trapaulin like tarpaulin, thank you for translations, Phil