Have a look at this
www.digitalcameraworld.com/cameras/camera-accessories/this-cheap-gadget-gives-nearly-any-camera-a-retro-waist-level-viewfinder-using-optical-trickery
I'm going to have to try one.
Waist level was always my favourite wat to shoot street. Back in TLR days. Tllt out screens have helped but I still don't like they push the camera out away from my body. I can imagine this device used with a wa lens of say 28mm plus a camera with good af eyesettings. Precise framing isn't essential for street photography, especially with something like a 28-35mm lens. Just crop in post production.