I bought a genuine nardi bosskit from ebay usa late last year. I don't know if you can get them new or anything.

The wheel will fit on a sparco/momo pattern bosskit but the boltholes in the nardi wheel are smaller, M5 or M4, not M6 as most wheels and the centre hole is larger than sparco etc so finding a horn button is interesting, Ive made up some alloy to sit in there on the racecar.