Not sure, but Whole Foods has like 30 diff kinds of salt (at the one near me, they're off on a display by the chocolate and cheese) of various colors and types, so you might try there.
pink salt... black salt... river salt... not sure about dendritic though.
www.fromnaturewithlove.com carries it. it is a very fine grain salt that has been crystallized to provide greater surface for f/o' and colors to adhere. reduces clumping. usage 5-10% mix color and f/o to this salt first and then blend into the rest.