You will still have access to "Software Sources" :
Synaptic > Menu line > Properties > Archives > > "Software Sources"
And can also open "Software Sources" with the command :
Code:
gksu --desktop /usr/share/applications/software-properties.desktop /usr/bin/software-properties-gtk
.. and also create a new launcher ( right click on the Desktop )
and copy / paste the above command to the new launcher.
But I don't know, how to edit the Gnome Menu to add it.
... KDE has 'kmenuedit'.
.....