The ornamental design for an adapter for eyewear, as shown and described.
FIG. 1 is a top front perspective view of an adapter for eyewear showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The dashed broken lines in the Figures show portions of the adapter for eyewear that form no part of the claimed design. The dot-dash lines show unclaimed boundaries that form no part of the claimed design.