Have you seen these?
http://www.volex.com/index.php?option=com_content&task=view&id=207&Itemid=58&lang=en
Or these?
http://www.iec-lock.com/
http://www.volex.com/index.php?option=com_content&task=view&id=207&Itemid=58&lang=en
Or these?
http://www.iec-lock.com/