Thanks so much! All good ideas. As a temporary work-around we found 70/30 sheets on sale at Thursday Morning and that might work out.
Yes, sheets are good, especially for trial garments. Bedding would be another category to check out at thrift stores. I have also (for special occasions and/or costumes) purchased fabric online from places that sell tablecloths and/or drape panels. Very affordable options for voile, satins, etc.