I can't remember what the stuff was called, but it's a material that someone would use under a dress. Real cheap, and works great - .50 cents a yard. I bought several yards, and use it every time I extract. Easy to rewash if you like, but I don't. It's just too cheap to bother with reusing.
And yes, I bought it at walmart. Not too hard to find in the fabric area. Looks like a cloth screen, and often comes in different colors. White is most common.
Sorry I don't have the name of it. If you must have the name, I'll go to walmart and find it.