The ornamental design for a support for tabletop of a side table, as shown and described.
FIG. 1 is a top right side perspective view of a support for tabletop of a side table showing our new design;
FIG. 2 is a bottom right side perspective view of a support for tabletop of a side table showing our new design;
FIG. 3 is a rear view of a support for tabletop of a side table showing our new design;
FIG. 4 is a front view of a support for tabletop of a side table showing our new design;
FIG. 5 is a right side view of a support for tabletop of a side table, with a left side view being omitted since it is a mirror image of the right side view from side-to-side;
FIG. 6 is a top view of a support for tabletop of a side table showing our new design; and,
FIG. 7 is a bottom view of a support for tabletop of a side table showing our new design.
The broken line showing of the table is included for the purpose of illustrating the tabletop, connector between the tabletop and the support for the tabletop, and the screw holes and screws connecting the circular connector and support to the tabletop, and forms no part of the claimed design.