Clip-on Flip-ups then flip it up and down as you need too. Can be used on clear glasses, or, if you need your sunglasses darker you can put these over you sunglass lenses. Size is 134mm wide by 47mm tall.
These sunglasses have been around many years. They are very useful and inexpensive. You simply pinch the cloth pin type clasp and slip it on to the bridge of your glasses. You can
Choice of 2 models: