take any paper (including a map you print from your computer at home) and brush on some deck water sealer (like Thompsons Water Seal), let it dry over night. you will be able to throw it in a sink full of water and it won't run. you can still write on it with a pencil. at home waterproofing for a fraction of the cost of commercial products. I bought a jug of generic deck sealer years ago and I've not even made a dent in it waterproofing hundreds of sheets.