The ornamental design for a gripping assist device, as shown and described.
FIG. 1 is a front elevation view showing the gripping assist device embodying the new design;
FIG. 2 is a magnified right side view thereof;
FIG. 3 is a magnified bottom plan view thereof; and,
FIG. 4 is a magnified top plan view thereof.
The rear elevation view is a mirror image of the front elevation view shown in FIG. 1. The magnified left side view of the design is a mirror image of the magnified right side view shown in FIG. 2.
The broken lines showing portions of the gripping assist device are for the purpose of illustrating environmental structure only and forms no part of the claimed design.