I work in downtown Chicago and need business formal clothes - where can I find them?

I just got a job as executive secretary for a CEO downtown and have been looking everywhere for nice suits and dresses that are affordable. Macy's, Kohls, Carsons, Penney's, Burlington Coat factory, Marshalls and H & M have very little. Even nicer stores like Anne Klein don't have much to choose from. Where can I find a decent selection of career suits and dresses?