Comfortable dress shoes?

I need comfortable shoes that I can wear to work (I dress business casual). I stand for long periods of time and walk around, and I find that even when I buy flats or shoes with a small heel, they seem very comfortable when I first put them on, but after a few hours my feet, knees, and back are all KILLING me. Does anyone have any recommendations on where to find shoes that are professional/cute looking, comfortable ALL day, and affordable? Thank you!!