i build a lot of my own equipment from home depot..
bands, i have some elitefts.net long bands. ironwoody.com has some good ones too.
chains, if you dont mind smaller chains, which means you need more of it, harbor freight is awesome. after using bands for a few months nowi would highly recommend getting the heaviest chain you can. like 5/8" or larger. that stuff is going to cost you $8+/ft. most places its twice that. if you are lucky maybe you can find some from the local railroad that has been stressed too much and you can get it free. or some from a scrap yard or crane graveyard.