The ornamental design for a container for shower waterfilter, as shown and described.
FIG. 1 is a perspective view of a new a container for shower water filter in accordance with my design;
FIG. 2 is a front side view of the new container for shower water filter shown in FIG. 1 in accordance with my design, with a rear side view being identical to the front side view;
FIG. 3 is a top plan view of the new container for shower water filter shown in FIG. 1 in accordance with my design;
FIG. 4 is a bottom plan view of the new container for shower water filter shown in FIG. 1 in accordance with my design; and,
FIG. 5 is a right side view of the new container for shower water filter shown in FIG. 1 in accordance with my design, with a left side view being identical to the right side view.