The ornamental design for watering can with a pump and knee pad, as shown and described.
FIG. 1 is a top-down isometric perspective view of a watering can with a pump and knee pad, displaying a knee pad containment chamber at the bottom of said watering can, a pump chamber located adjacent to the main fluid containment chamber and a first side mounted tool holding chamber.
FIG. 2 is a side elevation view thereof;
FIG. 3 is the opposite side elevation view thereof;