Storage Box for Cart

FIG. 1 is a top front perspective view of a storage box for cart showing my new design; FIG. 2 is a front view thereof and the rear side view being a mirror image; FIG. 3 is a left side view thereof and the right side view being a mirror image; FIG. 4 is a top view thereof; FIG. 5 is a bottom view thereof; and, FIG. 6 is a bottom front perspective view thereof. The broken lines shown in the drawings depict portions of the storage box for cart that form no part of the claimed design.