It's a shame the makers of the repro levers didn't use an 8mm fine thread as its pitch is 1mm (25.4tpi) and a 5/16" cycle threaded adjuster would have gone in, maybe with a cycle thread tap needed to get clearance on the long length of thread inside the adjusters. Goldies with clip-ons had welded on lever supports that had 5/16 Cycle thread in the lugs (I've just checked). You can get cables that fit these from George Prew, Address: Mill House, Royston Road, Barkway, Royston, SG8 8BX, Phone: +44 (0)1763 848763 George tries very hard for authenticity in what he sells. He has a passion for Rocket Goldies (as I do). George's web site seems to have gone so perhaps he is winding down his operation.
The pivot bolts used by BSA on the levers were 0 BA (6mm x 1mm pitch, same as nnormal ISO metric apart from the angle of the thread groove) when BSA made the bikes, but now 1/4 inch bolts seem to be supplied.
I hope that helps,
Jon