"I have seen glass shutters like the below that have frosted glass on a hinge but I cannot find any source to purchase these from"

Never seen nor heard of such a thing. No reason it cannot be fabricated by a local glass shop however. If they are telling you they have not heard of such a thing in my opinion it means they cannot be bothered. And in reality it will not protect in the slightest from humidity and really not much from water either.