I don’t know if anyone else is interested in a case to hold your gameshell or not but I today I bought a Nintendo 3DSxl/2DSxl case from Target for $10.00 The color matches my gameshell nicely and it fits perfectly. I used an exacto knife to remove the Nintendo branding and replaced it with one of the awesome stickers that came with the gameshell. I also removed a few stitches on the elastic that was meant to hold DS games and was able to use it to hold one of my micro USB cables. I have not tried putting the game shell in with the lightkey (mines not with me at the moment) but I believe you could fit that in the case as well. Anyways hope you enjoy, Happy hacking.
edit: you are actually able to store the gameshell with the lightkey in this case. more in the comments.