This is the case I have (and also where I got it from)
http://www.play-asia.com/SOap-23-83-...j-70-1by0.html
The front flap is velcro sealed and is just large enough for your DS to slide into snugly, and the material inside is kind of like the inside of a sweat shirt. On the back is a zippered section with designated spaces for 2 DS games and 2 Styluses, then an additional pouch. You can actually stuff quite a bit in there, I have a USB charger cable and a screen cleaner in there, but I've had GBA games and DS games and such in the pouch before.

USB Power cable
http://www.play-asia.com/SOap-23-83-...j-70-1ble.html
I actually have like 3 of these--2 are this one, and another one will work for both the GBASP(and original DS) as well as the Lite--but I got that from a different product.

This is what the 'cleaner strap' is like.
http://www.play-asia.com/SOap-23-83-...gxr-43-hl.html
One side is an image of something, and the other side is some kind of cleaning material for glossy surfaces--usually small screens. They come as freebies for different things in Japan, the ones I have came with a couple of games/accessories.