Two places you could try - either Campy Oldy, or Italian Cycle Products - mostly depends on whether you want the thinner locknuts for the older N-Record hubs, or the thicker ones for the newer C-Record hubs - getting the wrong ones will change your spacing by a few mm in case it matters. Campy oldy are more likely to do the old ones, Italian Cycle Products will probably only be able to get you the new ones. I think it helps with the newer ones if you can get the spare part order number from the service documents on Campags website. The track nuts themselves will pretty much be the same whether new or old.
Two places you could try - either Campy Oldy, or Italian Cycle Products - mostly depends on whether you want the thinner locknuts for the older N-Record hubs, or the thicker ones for the newer C-Record hubs - getting the wrong ones will change your spacing by a few mm in case it matters. Campy oldy are more likely to do the old ones, Italian Cycle Products will probably only be able to get you the new ones. I think it helps with the newer ones if you can get the spare part order number from the service documents on Campags website. The track nuts themselves will pretty much be the same whether new or old.
http://www.campyoldy.co.uk
http://www.italiancycleproducts.co.uk/
Good luck with it.