You will probably need to look for 1.1oz silicone impregnated nylon, or silnylon. Most silnylon comes in 60 inch widths (1.52 meters). What you would do is to cut 2 x 3.5 meter long peices of fabricand stitch them together on the long sides using a flat felled seam
. Then just hem the edges or add grosgrain ribbon for a more finished look. This would give you a tarp about 3 meters wide.