Build a miniature breath-powered steam engine that will fit in your shirt pocket.
Go to various metal yards and area machine shops and inquire as to whether they sell their offcuts/drops/scraps.
While inquiring, pull out your engine, fire it up and tell them, "I want to make some more like this but I'm having trouble finding materials."
Help them to carry the free material out to your car.
Take the next engine you build, along with a dozen doughnuts, back to the shop to show them what you've done. Drive there in a pickup so they'll have more room to load metal.