The ornamental design for diagnostic accessory, as shown and described.
FIG. 1 is a plan view of a diagnostic accessory that illustrates my new design;
FIG. 2 is a plan view of a second embodiment of a diagnostic accessory;
FIG. 3 is a plan view of another depiction of the embodiment of FIG. 1 in a different environment; and,
FIG. 4 is a plan view of another depiction of the embodiment of FIG. 2 in a different environment.
The broken lines are for illustrative purposes only and form no part of the claimed design.
The claimed design is a flat surface ornamentation of a diagnostic accessory, and is depicted in solid lines and includes the relative position of each crescent shape. It does not include the surrounding surface upon which the crescent shapes are shown.