The ornamental design for a hairpieceattachment, as shown and described.
FIG. 1 is a front, bottom, right side perspective view of a hair piece attachment which is positioned on the underside of a hair piece and shown in a concave orientation;
FIG. 2 is a bottom plan view;
FIG. 3 is a top plan view;
FIG. 4 is a front elevation;
FIG. 5 is a rear elevation; and,
FIG. 6 is a right side elevation (the left side being a mirror image).
The dash-dash line pattern on the hair piece attachment represents stitching. The dash-dash-long line pattern represents unclaimed subject matter only and forms no part of the claimed designs.