The ornamental design for a hairdresser's sink pillow, as shown and described.
FIG. 1 is a top, front and left side perspective view of a hairdresser's
sink pillow, showing my new design;
FIG. 2 is a front elevational view thereof with the rear view being
identical;
FIG. 3 is a right side elevational view thereof with the left side view
being identical;
FIG. 4 is a top plan view thereof, the bottom view being identical; and,
FIG. 5 is a top, front and left side perspective view of a hairdresser's
sink pillow showing a second embodiment of my new design. The sole
difference from the first embodiment resides in the corners being
chamfered.