They make vent caps for fuel tanks with a snap on cover/ lid. Bought mine on Ebay, got a dozen plastic vents for less than 10 bucks shipped. You need the correct size hole, they snap into place, mine have never leaked. Cover snaps into place, but will pop open when pressure builds. The have a raised rim around the edge so water cant run in. I use them in all my newer politically correct fuel cans and boat tanks so I dont have issues. As an old fart and a computor dummy, I am not sure howvto create a link ( think that is what they call it). Little yellow vent caps, not hard to find..the hole you drill must be a true 1/2" dia, if bigger the fent wont snap into place......