It's super easy to build a contact microphone to "electrify" your instruments. And I mean "instruments" in a very broad sense.

Just get a piezo element. Solder wires to it and connect to an amplifier.

My case is for a 20 mm piezo and is designed to be screwed in place. You can also fasten it with zip ties, Velcro or plain tape.

I use hot-glue to fix the microphone to the case. Try to minimize the amount of bubbles in the glue, since it can distort the sound.

The small tabs on top will hardly print, but is there to make velcro straps or tape stick better.