I have created a box with a lid to house the micro bit, a speaker which we picked up from tandy (it says 50FR on the bottom which might be the product code) and a pair of standard wires which would go down the corridors between the cylinder (for the speaker) and the cuboid (for the micro:bit). There are also supports for the micro:bit, space to plug in cables and a sliding lid which has a grille so that you can hear the music and a hole so you can see the LED display and press the buttons.
I made this project so i could have an all in one option for testing my music coding on the micro:bit. You can finf out how to code micro:bit music here: https://www.microbit.co.uk/musicfest/that-bass. Using 3d printing makes the project colourful and more of an ornament.