One time at my job we had some electrical work that needed done. The electrician had a small homemade switch box with a 120v mains plug running out of it and a switch on the front. The device basically threw whatever breaker that plug was attached to so he new which one needed work on and made the circuit safe. Where can I get one of those boxes, or a way I can trip the breaker from the outlet?
The answer which states that this is a bad idea is correct.
To answer your actual question: you could build such a device in about five minutes. Take an extension cord, cut it in half, attach the white and black wires to an ordinary light switch, and wrap the whole thing in a handy box.
When plugged in and the switch is closed, a short circuit is created that will either trip the breaker if it is working, or start a fire inside the walls if it is not.
That box should have been a warning that the guy was incompetent; it's a very bad idea. If the breaker malfunctions, it can start a house fire.
There are cheap devices available in most home centers and hardware stores which can put a signal onto the wire and pick that up at the breaker to identify which breaker controls that outlet. There's a better version that a pro should have which can do a few other things.
Or there is the traditional homeowner solution: plug a radio into the outlet, turn up the volume so you can hear it from the basement, and try breakers until you find the one which silences the radio.
That box works by connecting the live and neutral wires of the circuit to each other, i.e. it makes a short-circuit.
If all goes well, the fuse trips/blows. But as @keshlam said, it's a dangerous way to make a breaker trip: you're overloading the circuit. I did this once by accident, and had a 10 cm long flame blast out of the breaker box as the fuse tripped. Not the kind of thing you want to do on a regular basis.
The reason this isn't completely deranged at that industrial location is that certain industrial sites follow slightly more permissive rules owing to having on-site electricians with scheduled, proactive maintenance. You see this phraseology in certain NEC rules. Their work is done to a higher caliber than home wiring; THHN in metal conduit, no backstabs on the premises, frequent inspections, most circuits meggered, etc.
Doing this in a residential location with lax residential rules and work of unknown provenance is suicide.
Obviously the switch is basically dead-shorting the hot and neutral to induce a trip, but if you do that in a residence, you have about a 50/50 chance of inducing future arc faults at a backstab, or at the least, fusing it open. We get lots and lots of "plugged in a (well within legal range) large load and a backstab failed" questions. You also have a chance of other stupidity, like discovering why FPE and Zinsco panels are panela nongrata.
The safe answer to this would be to have an electrician install remote controlled circuit breakers, with a suitable trip circuit installed at the outlet where you want to remotely trip the breaker. (Eaton says they come in a CLR form factor for residential panels.)
Of course, properly labeling the panel, perhaps with a map showing where outlets/lights for each circuit would be a much cheaper and easier solution, and arguably more useful.