TeeDee mentioned this website in another thread, and as not to steal his thunder, I thought I would post the relevant info in it's own thread. This was the first time I had heard this site mentioned here on HF.
You can visit the website here:
Rockywood Outdoor Fabrics
Besides the polyester ripstop that TeeDee mentions I also noticed they sell Cuben Fiber, waterproof Cordura fabric (I think it's silnylon. JRB uses WP Cordura), a nice selection of zippers, as well as webbing and hardware.
I also noticed they have silicone coated ripstop in a variety of colors in both the 1.3oz and 1.9oz weights. It does say coated nylon so I don't know if this would qualify as sil. Maybe ordering some samples is in order.
I cursory glance at the site has turned up many useful materials at reasonable prices.