It’s one of those freshnel lenses you glue to your rear window to act as a fisheye lens. It’s actually surprisingly good. I can see the ground about 1.5m (5ft) behind me. I wish it would reach my rear bumper as that’s what I’d like to see but this helps!
Also, I took the picture with a poor man’s smartphone - my apologies.
From the inside I presume?
Can’t you attach it with a thin stripe of sticky tape along its edges, or sth similar?