The ornamental design for a headportion of a toothbrush, as shown and described.
FIG. 1 is a front view of a head portion of a toothbrush showing my design;
FIG. 2 is a right side view thereof, the left side being identical thereto;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a right, frontal perspective view thereof; and,
FIG. 7 is a left, rear perspective view thereof.
The dotted lines are for purposes of illustration and form no part of the claimed design.
The claim is defined by the solid line bound surfaces having various raised designs and the rear and outer surfaces of the elongated, tapered, oval ridge.