I was after some of these. I think www.twinspark.co.uk might be able to get them, but they won't be cheap. The easiest way would be to get some BMW lights and make them fit, then put an Alfa headlight protector over the front to make them smooth.
But if you look at the BTCC cars you'll see that the light's housing is constructed out of carbon-fibre. I'd say these were specially made for the series and they probably wouldn't be road legal anyway. Look damn good though I agree.