I know I am not the first to use a Nintendo DS case, but I don't recall ever seeing any mention of a model number anyone may have used.
Here is the one I use:
They have red, black (I wanted, sigh)
They have red, black (which I wanted ), some lime green color, a baby blue and a gray that I have seen.
Here is the inside:
The game slots are not big enough for CF cards unfortunately, so it isn't 'perfect' but you can put SD cards there. Of course, with some scissors, thread, and needle one could remedy this
It has a space behind thse slots where I can put my car charger, remote, and/or AC charger.
My SL-C3100 fits snugly and securely in the elastic strap, and there is room to leave a Wifi or Bluetooth card that sticks out in the unit while in the case.
Oh, I lied, I just stuffed a type-I CF card into one of the game pockets, but I will say that it is a very tight fit, and you risk damage to the pocket and I doubt you can put another CF card on either side of it.
I paid something like $8 or so plus tax at Wal-Mart. Sure, it isn't sleek, executive leather, but it gets the job done and is reasonably small in size The actual case I use for my DS is twice the size of it
Mine is black: