The ornamental design for clip-on sunglasses, as shown and described.
FIG, 1 is a perspective view of clip-on sunglasses showing our new design.
FIG. 2 is a front elevational view thereof.
FIG. 3 is a rear elevational view thereof.
FIG. 4 is a top plan view thereof.
FIG. 5 is a side elevational view thereof, the opposite side being a mirror image of the side shown; and,
FIG. 6 is an enlarged, fragmentary view of the clip-on sunglasses of FIG. 1.
The broken lines bound the places at which the fragmentary view of FIG. 6 is cut from in the depiction of the entire design and form no part of the claimed design.