NeoPiGamer

Here are the specs:

• Raspberry Pi Zero
• 3.2" SPI TFT Display
• Powerboost 1000C
• 1200mAh battery
• USB Stereo Audio Adapter
• 2.5W Class D Audio Amplifier
• Two 6mm Tactile Button Switches (for the additional Y and X buttons)
• Two Tall 6mm Tactile Button Switches (to repace the start and select buttons)
• DS Lite Mono Speaker (very nice sound quality)
• SPDT Slide Switch
• RetroPie 3.7

I used the pinouts on the gameboy advance to wire the original controls and buttons directly to the GPIO on the Raspberry Pi Zero. I cut the TFT display's controller board down to the size of the display and wired it directly to the Raspberry Pi Zero. Luckly, the waveshare drivers used for the display allowed for me to set the SPI speed high enough to get 60fps for silky smooth gaming. Every component used except for the power supply had to be modified in order for everything to fit inside the case. I get 3+ hours of battery life thanks to the energy efficiency of all components used.

Here are few build photos.