So I'm walking up some stairs with a friend of mine at a local movie theature and I spot the cylinder of a deadbolt lying on the ground wedged underneath a door frame. I say to him "Do you think anyone would mind if I purchased a real door stop from a hardware store and replaced that thing?" he asks why I want it and I explain I'm always looking for new/used locks to play with he then replies "You know when we do demolition (his family is in construction/demolition) we have a half a dozen locks we have to cut or just unscrew and throw away"
"really do you think your pops would mind if you saved them and gave them to me" "I don't think so we just toss them out and we have to pay for every dumpster full that gets hauled away anyway..." Long story short his father (the foreman) said it was ok and the next time they pull apart a building I'm getting all the used locks. Sweet deal huh? They might save a couple of bucks and I get free locks.
Like the story goes I'm a close family friend of the boss and bosses son (who works for him) so I don't know how many construction sites will be open to it but, it worked for me. : )