I've had some of my best luck at finding old/odd things at yard sales and older,small town hardware(or electrical supply)stores.These are disappearing in a hurry,so get out and look for them! Big-box places like Lowe's or Home Despot are driving them out of business altogether too fast. Befriend people who recycle old houses. Be up front and tell them what you want the stuff for-you'd be surprised at what might be put aside for you-free.
Visit the physical plant of older,smaller colleges,and again,be up front and honest.You might get to root thru a junkpile somewhere..Farm sales are the best. I'm on a very limited budget,and this teaches you to scrounge. The trouble with a lot of flea marketeers is they think anything that looks old is an antique, and overprice stuff. I think anyone who sets up a stall in a flea market should look up the words "antique" and "junk"-they ain't the same thing. Just a few thoughts. Scott