Home Depot? Dumpster diving? Man you guys are cheap! j/k, I've resorted to both those methods.
You've got to be resourceful in this hobby sometimes.
I just read the yellow pages for the 2 shops that supply my stuff. Neither of them advertise the fact they sell material, so maybe the yellow pages can be a bit misleading. One of them is a custom-machining/custom-manufacturing shop. Amazing what they have on hand. I love going to pick up material and seeing what projects they have going. Can't duplicate that experience with an on-line supermarket.