The ornamental design for a showerhead with holder, as shown and described.
FIG. 1 is a perspective view of a showerhead with holder;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left elevational view thereof;
FIG. 5 is a right elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is another perspective view thereof; and,
FIG. 9 is an enlarged view of portion of FIG. 1.
The broken lines shown in the figures are included for the purpose of illustrating portions of the showerhead with holder and form no part of the claimed design.