The ornamental design for a side panel for a shelf unit, substantially as shown and described.
FIG. 1 is a front elevational view showing the new design of my side panel
for a shelf unit;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a top plan view thereof, the bottom view thereof being identical;
and
FIG. 4 is a perspective view taken from the right side at the top front
corner of the shelving assembly column, the shelving assembly column
having the same appearance when viewed in perspective from the left side.