The USB port can supply 5V, but I needed the ~1.5V that a single AAA will supply.
I have used this setup for about a year now, and it works fine. If I had to re-do it, I would make sure that the wire lenghts for the original gadget wire and the power/USB wire match so you can tape the boxes together. Same goes for the direction in which the wires exit the box.
Step 1: Figure out the Circuit
If you have not worked with a breadboard before, you stick the parts into the holes, and the holes are connected to each other in rows perpendicular to the long axis of the board.
Please see the image for further instructions.
Measure your USB cable to find the ground/"-" and the positive.
I took the picture from several different angles, but could not find one that really made things clear. I hope the image notes do.
Step 2: The "Battery"
I only needed one battery for this project, but if you needed several, you could make dummy cells from a screw or nail that goes right through a dowel...
Step 3: Make it Permanent
I used an old chewing gum tin lined with electrical tape where it matters and some rubber grommets from an old hard drive to protect the wires from sharp edges on the metal. .