I've done quite well with a little ingenuity and by stopping at the odd scrap bin in industrial areas.
Pipes, truck brake drums, beer kegs, plate steel that turned into a sled, stones.
Make friends. Just this morning I got a new beer keg as a gift from the fellow that delivers my coveralls. Make people away of what you're after. You never know who's got a skidder tire in their back ally they want removed.
One mans junk...