Since this thread has been revived, a couple of follow-up comments:
There are now more services to do this sort of work. SendCutSend (available only to customers in the U.S.) now laser-cuts copper up to 0.250" (6.3 mm), and mentions busbars as one of the applications; they will also do limited bending and tapping... but they won't plate it, so that would be a separate process after the busbars are cut, tapped, and bent.And how about having them lasercut?
In The Netherlands there is a company that has up to 3 mm Copper (CU-DHP-R240) which they can cut. The challenge however is that single piece production is still quite expensive. Two of the same product is only a little more expensive than a single one. So it only helps if you can design in such way that you have multiple of the exact same busbars.
As the article in Electrical Engineering Portal noted, both copper and aluminum are normally plated with silver or tin, rather than nickel.If you are using Aluminum, you really should have it nickel coated, at least in the parts that are contacts, as Aluminum develops a resistive oxide coating.