I claim the ornamental design for a paint can topper, as shown and described.
FIG. 1 is a top, front, left side perspective view of my new design of a paint can topper with the components assembled.
FIG. 2 is a top, front, left side exploded view thereof showing the components in relation to a paint container.
FIG. 3 is a right side elevational view of the assembled components fitted to a paint container, the left side elevational view being a mirror image thereof.
FIG. 4 is a top, rear, right side perspective view thereof; and,
FIG. 5 is a top plan view thereof.
The dotted line representations of a paint container in FIGS. 2, 3, 4 and 5 are included to show environmental structure and form no part of the claimed design.