So I've opened up one of my Star Destroyers with the intent of lighting the engines, and while waiting for the parts to come in decided to try something else.
https://www.amazon.com/Groove-Cube-Smallest-Wireless-Bluetooth/dp/B014I0BZ7Y
Had one of these small Bluetooth speakers lying around. Once out of the housing, the PCB, battery and speaker fit perfectly inside of the Star Destroyer. Once I get the lighting installed, I will be able to glue it in place.
Here it a video of it in action. It's actually decently loud.
https://www.youtube.com/watch?v=nDuoEPOPY0g&feature=youtu.be
Edited by jp82729