I would argue that for modern street photography you don't need any sort of viewfinder at all. What you need is a camera on a neck strap. The camera has face recognition and auto everything except the shutter release. The shutter release is controlled from a wireless controller in you pocket. You also have a wide angle lens and enough good megapixels to crop ninety percent of them away. You wouldn't need to do much to a Pen to achieve that.