You could sit around a university campus, waiting for chips of material to fall off of buildings. Sure. It might even be fun.
Or, you could just donate lots of money to the school.
We traded a piece of Mojave Phone Booth glass for it.
The set came with a nice, full-color booklet, explaining each building from which a chip was gathered.
(Originally appeared in the Item of the Week section -- but it was, in fact, traded for a piece of Mojave Phone Booth glass.)