I think the most affordable, and most useful option is to keep your eye out for freebees and give away bags with corporate logos on them. I receive tons of these (don't have any at the moment, or I would PM you for your address)from various...
http://forums.treehugger.com/viewtopic.php?t=2515
Yes, it wears well, although you wouldn't want to leave it damp for long periods as mould would develop, as with any natural material. With backpacks, often it isn't the material that defines durability, it's the quality of the seaming, and...
http://answers.yahoo.com/question/index?qid=20090714012...
Canvas keeps on performing after years of use. There's no coating to wear off. Abrasion resistance is high compared to synthetics; it's natural fibers are more forgiving and pliable. If damaged, it's easily repaired with needle and thread.
http://www.acornbags.com/faq.html
Cotton Canvas Seat Covers are a combination of cotton and canvas, which make for a strong, yet soft and comfortable fabric.
http://beta3.autoanything.com/seat-covers/faq.aspx
Bottom line is 'yes' you can dye poly cotton in a washing machine, just as you would any other fabric. The down side is that it may not be the same colour throughout. So you have to decide if you like beige better than an uneven alternative...
http://www.blurtit.com/q975394.html
All of our Yoga mat bags are made from fabrics that are extremely durable. The cotton canvas bags are incredibly sturdy, water-repelling and have a very basic design. The loom-woven cottons (solid jacquard and traditional indian patterns) a...
http://www.barefootyoga.com/Page.bok?template=faqmatbag...
Yes, canvas is a heavy cloth made of cotton, hemp or jute. Has many other uses besides as a painting canvas.
http://wiki.answers.com/Q/Are_painting_canvas_made_from...