Kidsource. It's a teacher supply store but last time I went, they didn't actually ask for proof of Teacher ID. Or I lied. I can't remember.
http://www.kidsourcecatalog.com/adva...words=bean+bag (page takes a second to load.) They had several sizes and colours depending on what you want. If I recall, they are a vinyl material and definitely heavy duty construction as its meant for young children to abuse in the classroom.