Hobby Lobby. Online sources: Denver fabrics, FabricMart, HomeSew and others. One problem is getting into shipping expenses on some of those.
Actually also try WalMart, because they have some surprises there. They have lots of pre-cut, stable knits that are $2-6 for 2-3 yards.
Some thrift (Goodwill?) stores also sell fabrics, and you can watch for fabrics in estate sale/moving sale-type ads.
Another option is finding large garments made of lovely fabrics, at Goodwill/thrift stores, and cutting them at the seams to recycle the fabric.
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.