I plan to make one eventually. Tarps and some G4 packs are my next projects.
I came across some 1.1oz SilNylon remnants for VERY cheap (<$1 yd)
so I bought all they had except blaze orange. Most pieces are 68" wide by 68" -180" long. Unfortunately, the colors are red, blue, yellow, etc., but it was cheap.
I also bought some 1.1 ripstop with DWR finish in OD green, about 50'x68" wide for less than 1/yd.