The ornamental design for a portable supportpillow, as shown and described.
FIG. 1 is a perspective view of portable support pillow showing my design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a rear elevation view thereof;
FIG. 8 is a perspective view showing portable support pillow in use by an individual; and,
FIG. 9 is a perspective view of the portable support pillow in collapsed, rolled condition and connected to a piece of luggage.
The broken line showings of a tether string, grommet and snap fastener elements in FIG. 1 of the drawing, the passenger seat and seat belt in FIG. 8, and the luggage in FIG. 9 of the drawing are for illustrative purposes only and form no part of the claimed design.