Summary

This is an arcade joystick I designed. I based it on the Neo Geo AES joystick.

Materials required and where to get them:
4 - 8 1/4" pins, auto parts store or online
6 M3 socket head screws, hardware store or online
2 24mm arcade buttons, online
7 30mm arcade buttons, online
1 USB encoder, online
1 Arcade joystick compatible with SANWA mounting plates, online
Double sided tape, hardware store or online

Raspberry Pi version:
USB Splitter, online
15 ft micro USB cable, online
15 ft HDMI cable, online
<=1 ft HDMI cable, online
HDMI female to female connector, online
Raspberry Pi, online (Preferably 2 or 3, as some games that actually work well with the controller slow down even the Raspberry Pi 3 Model B (Not B+))

Daisychain version:
USB Splitter: online
USB Extender (About 2 m for original cord length), online

You can find skins for the control pad at http://pixarchive.freeforums.net