Here's a link to pictures of appliance connectors - the appliance ends.
http://quail.com/iec.cfm
The one you describe does not appear to appear in the drawings - others on here describe similar problems to yours - nobody seems to be able to provide an answer.
Your main challenge is to identify the connector reference - if there is one. Is Sona an Italian company? if so C5/C6 style is an Italian connector I believe.
Wikipedia has a short article with photo's
http://en.wikipedia.org/wiki/IEC_connector
Good luck...
Peccavi
July 2009