I use a little "mini folio" case for the Nintendo DS. I noticed last month that the DS is similar in dimensions to the N800, except quite a bit thicker. My DS case holds my N800, my bluetooth keyboard, an extra battery, my GPS unit, and my headphones, all in a little package that's smaller than my wife's change purse. Granted, my wife has a big change purse, but still...

Oh, and since the DS is also a touchscreen, it has a spot for your secondary stylus and it has a little screen cleaner rag attached on a ring.

I bought mine at WalMart, but I could really only find a few places online. Amazon offers them for $10.

Here are some pics I found around the net. Mine's a plain navy cloth colour (no Mario star or anything ).