@Treflip: No, but I have a 3D printer at work
@Drakker: The SD card is in there, below the screen... but I forgot to put the hole on the side(!) Yes, it can use the Gamebuino libraries. The Gamebuino is an Arduino with a screen and SD card, its quite easy to make your own. Battery is still missing, because my LiPo cells got stuck in China post (they are very careful nowadays with shipping LiPo).
This project started so that I began building 2 copies for my 2 boys. And since I grew up with the "original" portrait-style Gameboy, that's where my heart is
I've also tried this with 3xAAA batteries, and I can fit them in, and I am still considering it. Only problem is that I haven't found a suitable holder for AAA batteries yet.
This is still through-hole components on a perfboard, and a real pain to solder and get to fit in such a small space.