[0]https://www.pi-supply.com/product/raspberry-pi-3-model-b-new...
[1]http://www.nes30.com/
[2]https://www.raspberrypi.org/blog/lego-nespi-case/
Im also thinking might be able to use authentic controller but cut of the connector and instead wire directly to the Pi's GPIO.
[0]https://www.pi-supply.com/product/raspberry-pi-3-model-b-new...
[1]http://www.nes30.com/
[2]https://www.raspberrypi.org/blog/lego-nespi-case/