The ornamental design for handle for suitcase, as shown and described.
FIG. 1 is a perspective view of a handle for suitcase showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right view thereof; the opposite side being a mirror image of the shown;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is the perspective view embodying the utilization of handle for suitcase in which the broken line is for illustrative purposes only and forms no part of the claimed design.