The spa industry is aiming to expand clientele. During "Spa Week," an April 16-22 industry event for the $13 billion North American spa business, some 400 spas in 22 markets in the U.S. and Canada will offer $50 treatments. Sponsors include Allure magazine, Contrex Water, Aquafresh, NicoDerm, Michel Torino Wines and Cosmetic Executive Women.