The ornamental design for a snow pusher shovel, as shown.
FIG. 1 is a perspective view of a snow pusher shovel showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof; the left side view being symmetrical thereto;
FIG. 4 is a back view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.