GUID and ID of the toolbar context menu

Currently I want to add a new menu item to the toolbar's context menu. "Add item", which is similar to the default "Customize..." 

To do this, I need to find the ID of the context menu (plus GUID, if possible). 

The vsct file content:

<CommandTable xmlns="http://schemas.microsoft.com/VisualStudio/2005-10-18/CommandTable" xmlns:xs="http://www.w3.org/2001/XMLSchema"><!--  This is the file that defines the actual layout and type of the commands.
        It is divided in different sections (e.g. command definition, command
        placement, ...), with each defining a specific set of properties.
        See the comment before each section for more details about how to
        use it. --><!--This is the file that defines the IDs for all the commands exposed by VisualStudio. --><Extern href="stdidcmd.h" />
etc.....<Group guid="guidMyPackageCmdSet1" id="ToolbarContextMenuGroup" priority="0x0600"><Parent guid="guidSHLMainMenu" id="????????????????" /></Group></CommandTable>

The id should be the toolbar's context menu's. For example, the code editor's context menu id is IDM_VS_CTXT_CODEWIN. Any words of wisdom appreciated guys!