I have not, but it should be the same as tapioca powder. I know it by yucca, but here it is called tapioca or cassava instead.
I buy it at the grocery store if making Brazilian Cheese bread, or at Makeyourown or another soap supply store when using for cosmetic/ bath products.
I always think of that plant as Flor de izote, the national flower from El Salvador (edible) but I think it is a different plant from this one. As Izote only blooms once a year. I have never seen either it sold as powder though.