I would look hard at starite s.t.e.p. "motor over" cistern pumps. They claim very high efficiency and you can get 120 or 240 volts. The prices are amazingly small for a motor over pump [apparently the first on the market] and can be run on a small inverter.
I believe a site called worldwide power and pump in Florida will come up on your search and give you a good start. The shurflow is weak on life span, and the grundfos absurdly high in cost. If you use it, please post back because it looks like a great piece of work for storage tanks and DC converter app's.
Notice that this pump would be set IN your tank, and pushing water out is much more efficient than any suction based pump.
At 40 gallons a day, this 1/2 hp pump will run for just a few moments!
I noticed noise concern: the pump set in the cistern will be noiseless and since you are offline, the huge advantage of a submersible pump should be very attractive, even if you need run a wire to the cistern and remove the footvalve [you get a free checkvalve in the pump head]