The materials are very easy to find, you should be able to get them at any decent outdoor store, or anywhere that sells climbing equipment. And the best news is you should already have your most expensive piece of equipment: your camera! All you will need now is a few feet of 1" nylon webbing (enough to make up about 3/4 of your total strap length, its better to be too long here than too short, since you can shorten it later) and about 2 feet of thin, light rope, both of which should cost little more than a few cents per foot.
You will also need the knowledge of a few useful knots, which i will be providing.
For more information on knots and lots of other useful knowledge join the Boy Scouts. Pictures of my Troop can be found here