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Map holders are a thing

Classical paper maps yes. I manage to trash them after one hike even without rain.

But nowdays you get them coated in a plastic layer ... very nice, water proof and durable.

edit: or like the othe commenter mentioned, it is not a plastic layer and rather plastic itself called Tyvek or similar

Most of my hiking maps are printed on Tyvek or the equivalent.

And in any case a map is a piece of safety equipment - you spec if for the worst case scenario.