The ornamental design for a hair accessory, as shown and described.
FIG. 1 is a perspective view of a hair accessory, showing an exemplary embodiment of my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an environmental view thereof.
The broken lines shown in the Figures depict portions of the hair accessory that form no part of the claimed design, fabric stitching of the hair accessory that forms no part of the claimed design, or an environment of use that forms no part of the claimed design. The shading shown in grayscale in the Figures represents contours and does not claim surface ornamentation or treatment.