The ornamental design for a grippingcover for grabbar, as shown and described.
FIG. 1 is a front perspective view of a gripping cover for grab bar showing my new design;
FIG. 2 is a top view of a gripping cover for grab bar;
FIG. 3 is a front view of a gripping cover for grab bar;
FIG. 4 is a right side view of a gripping cover for grab bar; and,
FIG. 5 is a bottom view of a gripping cover for grab bar.
Left side views not shown are mirror images of right side views. Any broken lines illustrative of environmental structure in the drawings are not part of the design sought to be patented.