The ornamental design for a surfaceconfiguration of a portion of a rearbumper for a vehicle, as shown and described.
FIG. 1 is a left perspective view of a first embodiment of a surface configuration of a portion of a rear bumper for a vehicle according to my novel design, the right perspective view being mirror symmetrical; and
FIG. 2 is a front view thereof.
FIG. 3 is a left perspective view of a second embodiment of the surface configuration of a portion of a rear bumper for a vehicle according to my novel design, the right perspective view being mirror symmetrical; and,
FIG. 4 is a front view thereof.
The broken lines are for illustrative purposes only and form no part of the claimed design.