How to build a "Fridgebeats"

Hello Community!

I would love to build one of these fridgebeats by myself. If you've seen them on tiktok you know what they are, but here is their website: https://fridgebeats.com/

It is essentially a battery, button, box, PCB and speakers. I'd love to find a way to make one for less than $20 in parts, but I'm unsure if that's possible. I've built an emulator from an old gameboy shell and using raspberry pi, etc, so I'm not new to builds like this, but I would love some help getting started.

Any help would be amazing, thank you!