I have one of these

http://www.hori.jp/products/dsl/dsl_...uch/index.html

It fits around it snugly, and the material on the inside actually wipes it clean when you put it in/take it out. I dont' use it much really, cuz the pouch itself doesnt' fit in my pocket, but if i'm carrying it in my bag or something I stick in there. My Navy Blue DS lite comes out spic-n-span.