deck fill

My boat never had a water fill, and I'm tired of lifting up the cushions and bringing a hose into my boat in order to fill up the fresh water. The issue is really the vent where the water will overflow. Currently the tank vents to the cockpit locker. I guess the ideal option would be to plumb...

The cap appears to be 1.5" with a pitch of 11. Does anyone no of a source for a replacement cap?

I absolutely deplore the caps on my deck plates. Instead of being keyed for the usual deck plate tool, some idiot decided that it'd be a great idea to key them for a standard winch socket, so you use winch handles to open and close them. One sunk winch handle later, which I dropped as I was...