The ornamental design for a toiletplungerholder, as shown and described.
FIG. 1 is a perspective view a toilet plunger holder showing my new design, the broken-line disclosure of the plunger being for illustrative purposes only and forming no part of the claimed design;
FIG. 2 is a front elevational view of my design;
FIG. 3 is a back elevational view of my design;
FIG. 4 is a top view of my design;
FIG. 5 is a bottom view of my design; and,
FIG. 6 is side view of my design, the opposite view being mirror image thereof.