Amazon has both crocus cloth and emery cloth. The difference may be in the type of abrasive used. 600 grit is a fine grade and seems to be what Amazon labels as crocus cloth. Emergy cloth on Amazon comes in different grits, with 800 grit being super fine. The "cloth" part just means that the sanding medium is backed with cloth rather than paper, making it more bendable. I'm thinking anything 600 grit or finer with a cloth back would be fine for a sewing machine. Amazon offers these in bulk sizes. I think you could get just one sheet from a local hardware store or hobby store for considerably less.