Honda CRV towing mirrors

I think I am right in saying that towing mirrors are compulsory/recommended when towing overseas. Bearing this in mind, I have a 2009 Honda CRV and have had problems getting towing mirrors to fit. Could anyone recommend a manufacturer and model of mirror to fit as I have been ordering ones online only to end up sending them back as they will not fit. I personally think that the cars standard mirrors do the job without extending them but would not want to fall foul of the law while we are away so any advice would be very much appreciated.