These are exactly what I have been looking for!  I have rimless glasses, which I must wear to drive, and the clip-on sunglasses currently available in stores clip onto the frames of glasses, so I am unable to use them.  Plus, I don't like them because when you take them off, you have to put them away or hold them.  These clip-on lenses simply flip up and out of the way, which makes it much easier when entering an indoor or shaded area.  I was so happy when I searched and found that this type of clip-on is still available via the internet.  Bravo!