How to obtain a new "ariel in" socket for my CDR 2005 VDO (Vauxhall Corsa)?

I have acidentally damaged my ariel (FM?) in socket at the back of the above head unit by attempting to force a different sized one in from an FM Modulator. It forced one of the metal connecting strips downwards and now my radio quality isn't as good. I have tried lifting this strip up with tweezers but it's too small. I now need a new plastic replacement bit (that sits insude the metal bit) so as all points are connected with the FM line in (RF Signal).

Any help would be much appreciate, at the moment the only option I can see is getting a whole new HU to get decent quality radio back!!

Cheers