NOTE: You don’t need a switch, or the leads for the battery. If you just have the 9v battery and the clip, you can just expose some of the wires at the ends of both the red (positive) and black (negative) wires. Then when you want to power the circuit just slide them in the appropriate power lanes. You will want to wait until the final steps to do this though.
NOTE: I like to use an alligator clip to the speaker and on the opposite end use the other alligator clip to clip onto a jumper wire. Then I can use the jumper wire to go into the breadboard without having to solder or cut anything.
NOTE: You can watch this tutorial on how to fix headphones to get a better idea of how to make your own. Or you can strip a cheap pair, just try to use a mono jack.