You can buy the lights from a main dealer for not much money. I went to Ross Peters at Meridien Modena and they were about £12 each plus VAT and postage. The part no. is 383100111. <= correct part number now
Fitting is easy, you unscrew the chrome and colour-coded plate, then unclip the connector in the power wires to the lights, then simply unscrew them from the plate. The only issue is that the screws are not galvanised so are probably rusty, and the replacements don't come with screws. I bought some new, black anodised screws for a better look.