Look at the Coverlite material Tom Yost uses. (www.yosterks.com) It is commonly used for truck tarps, and very tough.
Price is a bit more than cotton duck, but you don't need paint or filler, and it doesn't get mildew or rot. You can sew it, or use glue, or do both.
Cotton duck (canvas) for kayaks and canoes is available by mail order from www.clarkcraft.com at a reasonable price. Mauritzon, in Chicago IL, sells the Coverlite fabric. Yost's website has ordering details.
Some people have covered their kayak frames with clear vinyl. Wal-Mart sells this for under $4 a running yard at almost all their stores. For a 16-foot boat that would mean 5 1/3 yards, or about $22. It won't last as long, but the clear material is an eyecatcher, you don't need to paint it, and you can assemble it with glue, or staple it to the gunwales, so it's fast to skin the boat. For the price of a quart of boat paint you could reshin the boat with the clear vinyl every year!
Hope this helps.
PGJ