The ornamental design for a handle holder, as is shown and described herein.
FIG. 1 is a perspective view thereof;
FIG. 2 is a top elevational view thereof; the bottom elevational view being a mirror image thereof;
FIG. 3 is a right side elevational view thereof; the left side elevational view thereof being a mirror image thereof;
FIG. 4 is a front plan view thereof; and,
FIG. 5 is a back plan view thereof.
The broken lines in FIG. 4 illustrate portions of the handle holder and form no part of the claimed design. The handle holder is shown with a symbolic break in length. The appearance of any portion of the article between the break lines forms no part of the claimed design.