i did find the unbleached waffle muslin at joanns.. it is no longer available on line, or in some joanns. it runs 53" wide.
i didn't get it, because i really wanted white. it may be worth getting a yard and trying it out..here are some reviews of the waffle muslin from joanns:
http://www.joann.com/joann/catalog/reviews.jsp;jsessionid=321EA2B578FF7E1305E7C963817BDE1C.a2p1? _DARGS=/joann/catalog/productdetail.jsp.1_A&_DAV=atg.servlet.SessionName Context%40f2fe5d4&_dynSessConf=-8195858639634060395&pageName=&CATID=cat2555&PRODID =prd36712&product=true&supercatId=