Simple Pump: 12v DC electric motorized pump.
Now or later. Ideal for Solar. 5-min installation.
Recommended Configuration for Motor
Booster pumps designed specifically to pump into a pressure tank are available from a number of vendors (e.g. Dankoff, Surflo and Jabsco), many for under $150 (US).
Such booster pumps include an integrated pressure sensor. It signals the booster pump to turn on and off, according to a target pressure. The Simple Pump would then be controlled by a simple float valve in the reservoir tank.
Configuring in this way increases the depth from which you can pump with Simple Pump's frugal, low-power-draw motor, and increases the life of the motor... an important consideration in an off-grid or backup application.