Most quilt shops carry it. You will not find it at chain places like JoAnne, Hobby Lobby, Hancock's etc. Your best bet is to order on line. Just put "retayne" in a google search engine and you will get loads of hits. Like Amma said, Dharma trading carries it
http://www.dharmatrading.com/
There are vendors for it on Amazon.com and loads of crafting supply sites.