FWIW the ETK, which is a few years old, says:
HAND BRAKE BOWDEN CABLE P/N 34411162005 $37.67
It's probably a few dollars more now. But that's list, and I suppose you'll get a BMW CCA member discount (not a member?). I recommend the BMW Store in Ohio for mail order.
Never did this job so I can't help with the task estimate.