Retro Raspberry Pi systems are really fun builds for the incredibly inexpensive single board computers. You could start from scratch, or for a leg up on a “no frills multi system emulator that fits in your pocket,” the Game Boy Zero provides a quick and easy head start.
The image above shows many of the choices Eugene has provided for his design. It is available as just a PCB with your choice of three different colors. From there, choose which components you want sent along with the order. There’s even a fully assembled option if you only want to work on soldering your Raspberry Pi Zero to the board before the gaming begins.
As shown in the image below, it can even be housed in a nice layered plexiglass case. This enhancement isn’t currently for sale, so you’ll need to make or source this yourself based on the design found here.
You can see the device’s creator, Eugene Andruszczenco, going over how to install an optional USB soundcard to the device in the video below, giving you a good idea of the size and feel of it. He’s got a lot more videos on this playlist, so be sure to check them out if you’re thinking of buying one of these or even building something similar from scratch.