hmmm. the only thing I could think of, would be to make a replica of Peter's whole outfit (every...last...piece)....in dark grey. Then, you'd have to paint your face with the same shade of paint.
Whether or not you'd be recognized as his shadow; is chancy. Maybe you could get a friend...relatively the same height as you...(or taller)...to dress as a regularly costumed Peter and walk in front of you all day.