You can, indeed just Google "fog city". They are a plastic inner shield, that attaches inside your visor to provide an air space. They are also photochromic (self darkening) but most UV protected faceshields will prevent this from working well. There is a good
article on WebBike World that explains them. Sometimes a little hard to find, but getting better. My first ones had to be sent to me by a friend in Canada. They are made in Italy. My BMW shop carries them now. I have seen them available on Amazon, too.