I googled "prepared for dyeing cotton fabric" and got these among other sources:
http://www.dharmatrading.com/fabric/...d-45-inch.html Also source for dyes, tools, etc.
https://www.softexpressions.com/soft...abrics/PDF.php 2 fabrics here, one of which is what Hoffman uses for their batiks
https://www.softexpressions.com/soft...abrics/PDF.php Here it is organic in several formats at 2-3x the price.
http://www.joann.com/kona-twill-prep...n/1103787.html Kona TWILL Prepared for Dyeing at Joanne's by the bolt
Jan in VA