My box call isn't an expensive model, but I've always just slipped it in an ankle sock. Makes for a nice conforming fit due to the elastic which keeps it slim and from making noise when I don't want it to. Not exactly waterproof, but it keeps the moisture away. Works well for an el cheapo like me. You could always double up the sock for an extra layer or put a wicking sock liner inside it. If it's gonna be exposed to more water than that I'm leaving the woods unless in a blind.