I make a lot of my own stuff, and finding the fabric to do it is always expensive, particularly when there is a learning curve.

Pro-Tuff Outdoor Solid Fabric, Black - Walmart.com

This stuff is available at walmart, and in several colors other than black. I bought a roll to make slip covers for my work van, and they are holding up really well.
Also made this out of it, its not ultra light fabric but lighter than cordura, and pretty tough.
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Ive made some frame bags out of it, and its about like cordura, but at under six bucks a yard.