How to restore accidentally deleted system tray Desktop Settings icon?

[Juan R. de Silva]

On Tue, 22 Jan 2013 21:19:31 -0500, Clay Weber wrote:

> That is not part of the system tray, it is the Show Desktop widget
> (minimizes all open windows to show the desktop). You can get it back by
> right clicking on the panel somewhere, select panel options and go to
> the Add Widgets tool, search for show desktop, then drag that to your
> panel somewhere.

As I just mentioned in my response to Cody Smith, this widget after I by 
mistake deleted it is not in the Add Widgets tool list anymore. This is 
the problem. I just cannot find it anywhere.