Unless you have a LBS with a long history or one that happens to be a Sturmey Archer dealer you'll probably need to go to the internet.
Harris Cyclery has a bolt-on anchor for $2.95 that could (if I understand your need correctly) be the solution. They also have some NOS replacement cables as well as modern versions depending on how much you are willing to spend or how much you value authenticity.
They are also available on eBay on a pretty regular basis.
Good luck and enjoy the bike. I regularly ride a '67 Schwinn Racer and a '47 Schwinn Continental, both with 3 speed S-A hubs. They're both great fun.
Regards,
Alan