Eye patch for target shooting

What's happening?

So my friends and I went to do some shooting. Dressed as Raoul Duke from Fear and Loathing, one of the guys decided to use an empty chips bag as an eye patch for target shooting. A Thoughtless Act, which helped him with his aim. 

Design solution

The shooting glasses he's wearing, has yellow glass. This helps the wearer to see the contours of the woods and thereby spot the animals, he's hunting. When spotting animals, it's important to be able to use both eyes. And then, when you've spotted the animal, the shooter would want an eye patch to help the aim. 

A possible solution could be a pair of glasses with switch glass. Since it has to be easy and fast to flick it on and of. Then you could flick on and off the glass by squeezing the temple bar.