The ornamental design for a container insert for use in a lotion applicator, as shown and described.
FIG. 1 is a side elevation of a container insert for use in a lotion applicator showing my new design;
FIG. 2 is a top plan view of the container insert for use in a lotion applicator shown on a reduced scale; and,
FIG. 3 is a cross sectional view of the container insert for use in a lotion applicator shown inserted into the handle of a lotion applicator shown in phantom lines.
The broken lines showing a lotion applicator handle in FIG. 3 are for illustrative purposes only and do not form part of the claimed design.