It is a pain to try to get just a small quantity of anything to do MYOG projects, so I try to keep my eye out for sun shades made out of reflectix(the type used in cars to reflect the heat) whenever I am in a thrift store. You can usually pick one up for a buck or two and get enough material to make at least 2 cozies.
The same can be said for buckles & webbing. Most thrift stores probably have a few backpacks, duffel bags, etc for sale. Not always, but sometimes.