The ornamental design for a mirrorattachment, as shown and described.
FIG. 1 is a front perspective view of a mirror attachment according to the present invention showing a mirror disposed within the mirror attachment in the open position;
FIG. 2 is a front perspective view of a mirror attachment with the mirror in the closed position.
FIG. 3 is a front perspective view of a mirror attachment without a mirror in an open position.
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a right side view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a bottom view thereof.
The mirror and stand shown in broken lines forms no part of the claimed design.