The ornamental design for a supplementalhairpiece, as shown and described.
FIG. 1 is a top plan view of a supplemental hair piece showing my new design;
FIG. 2 is a side elevational view thereof;
FIG. 3 is a bottom plan view thereof; and,
FIG. 4 is a top view of the supplemental hair piece as it would appear in use.
The supplemental hair piece is shown on a reduced scale in FIG. 4. The broken lines shown in FIGS. 3 and 4 are for illustrative purposes only and do not form part of the claimed design. The unshaded interior surface in the middle of FIG. 3 does not form part of the claimed design.