My solution was to go to Academy Sporting Goods and buy two, blue 2.5 gallon water jugs. One of these will just fit through the opening under the flip up counter in the 23.5 galley area. These come with a screw in tap in the lid.
I then went to Lowes where I bought a brass male garden hose fitting with the usual male nipple which fits inside a hose. I unscrewed the tap from the water jug lid and epoxied in the male hose fitting. I attached plastic hose to the the protruding nipple and reattached the jug lid, now with male hose fitting on the top and plastic intake hose on the bottom, to the jug.
I mounted a female garden hose connection to the hose going to the sink pump, and then screwed together the male and female garden hose hose connectors. It worked perfectly. I bought a female cap which fits the male hose fitting so I don't spill water when getting a full jug into the space under the sink.
I installed two eye fittings to the inside of the galley molding, on either side of the water jug and use a shock cord hooked to the eyes and around the jug to keep the jug in place when heeled on starboard tack.
For my short over night trips I find 2.5 gallons over water is plenty and I carry a the spare jug just in case. I did not modify the lid on the second jug, I just swap lids when changing tanks.
This was a simple solution to the water bag, with the benefit the jugs are easy to take home to clean at season's end
Kind regards
Hugh