Abel Baker cycles are worth a go. I've forgotten the name of the chap, owner I think. tel. 01279 758718.
Been a few years since I was in touch, but he was making repro small spares for a lot of vintage parts. Only issue can be getting hold of him, and then him actually sending them out. Nothing malicious, he just lost my address a few times! Then I missed his latest batch and had to wait for the next batch of cones to harden!
I got spares for old Campag Gran Sport as well as Airlite hubs. It was very old school, no upfront payment, just an invoice on receipt of parts! They were pretty good too. Also had a good chat to him on the phone a few times, think he was even making repro Brampton headsets.
Alternatively, you could try Mick at Madgetts Cycles. He helped me with some small vintage parts when getting a frame resprayed. Don't think he really keeps a stock of such things though. He's pretty quick to email back though whenever I've dropped him a line. Very nice chap.