The signature plaid is hardly square these days, as bikinis, leather pants, and messenger-style bags join the traditional gabardine trench coats. The flagship store on East 57th Street is the mother lode; the SoHo branch has an abbreviated assortment. Subway: N, R, W to 5th Ave./59th St. Other location: 131 Spring St., between Greene and Wooster Sts., SoHo, PHONE: 212/925-9300; Subway: R, W to Prince St.