If memory serves, they are a one-off custom made set. As David P suggests, the basis for them was indeed a standard Alfa wheel. I'd hazard a guess the basis was the 17" teledials. I seem to recall reading a while ago (I think it might have been on here too?) about someone who had made contact with the owner/creator to talk about buying them, but they weren't at all interested in selling. As for where you'd have a set made - I'm not really sure, you could try to get in touch with a wheel manufacturer to see if they'd be interested in creating a set for you? I'd imagine this will be rather expensive though, unless you can put together a group-buy? I don't know what else to suggest really, other than to do it yourself!