Well, I looked everywhere to find the music box. I suppose not literally everywhere, but I found myself searching obscure websites. From Chinese wholesalers to upscale artisanal music box makers. I even emailed a few people on Etsy, but was forced to select from a limited selection.
So I'm building it myself ヽ(´ ー｀)ﾉ
There are still a few things to work out, most notably:
The gear mechanism is of poor quality.
Made of cheap plastic that a gear has already been stripped clean. I've replaced it, but saying it's a delicate process would be an understatement.
There's a weird buzzing that occurs during playback.
This should be an easy-ish fix. In the video, you can see I'm pressing down to help with the buzzing.
Everything must be mounted within an actual box.
Sheet music needs to be taped together to create a continuous loop.
Finally, solder everything to an actual breadboard.
After finding the sheet music online and marking the notes, the process went like this:
Step 1 - Punch the notes out.
Step 2 - Wire everything up!
Step 3 - Add some code!
Normally, I would create a whole repo for the code used. But for now, this is all there is.