Why not a RetroPie project portable that can be also connected to a TV and played like a regular Raspberry?

I'm not the best to 3D design, but it works for me. But if you want to change anything I'm also sharing the .f3d file for Fusion360.

Used a 4,3" composite screen soldered directly to the PP24 and ground video in PP6.

PP25 and 26 for sound output. A PAM8403 is used for audio amplifier.

Then, a PS3 controller is used inside and soldered directly to USB and tactile buttons

When you want to play on TV, just plug it directly to the HDMI and be happy!

Material List:
Disclaimer: These are not exactly the link where I bought, is just a model. So you might find cheaper

• 4,3" Composite Screen
  https://goo.gl/qYfAMf
  Some composite screens are made for 12V but works with 5V.

• XL6009 Step-up voltage converter
  https://goo.gl/x2Qboc

• Mini Audio Amplifier PAM8403
  https://goo.gl/ZWpwT3 (You migh want to take off the header and connectors to solder directly to the board and save space)

• A mini power switch like this
  https://goo.gl/ZKmFya

• PS3 Chinese controller
  https://goo.gl/Mp4Ng2 (Using just the board)

• Some tactile switches (14, i think)
  https://goo.gl/H8LfvQ

• Prototype Solder Board
  https://goo.gl/Yfw4eF

• TP4056 Battery charger with protection
  https://goo.gl/jh6wwe

• 4x 3,7V 18650 Battery
  https://goo.gl/FveduX

• Green and red 5mm LED's (soldered in the Battery Charger)

• Raspberry Pi 3

[EDIT: 06/02/18]

I had some problem with the chinese PS3 controller board. So I replaced it for a Arduino Pro Micro (32u4 chip, the same as Leonardo) as you can see in the last picture.

The code used in the Arduino controll is in the files!

This is the library I used: https://github.com/gamelaster/ArduinoGamepad

Instructable made by the guy who made the Library: http://www.instructables.com/id/Arduino-LeonardoMicroATMega32u4-As-GamepadGame-Con/