There are millions of old classic, superbly built bikes just looking for good homes. I bought a vintage Italian racer from a bike shop for £40 and haven't spent anything on it after a thousand miles or so. Some of the 70's 80's bikes are so well built, usually well maintained, are such good value and have an aura about them that new bikes just don't have.
Try a wanted ad in your local paper and scour the local bike shops etc. 531 or Columbus steel butted tubed machines are great, very light and strong.