I know I've mentioned it before, but for NOS, re-manufactured and reproduction Buffalo parts (quite a few stainless fittings), including NOS exhaust pipes, GTReiner in Germany has about the best selection I've come across. An NOS exhaust system will make a very fat wallet thin

, but if its a restoration you are doing then at least its an option to consider. He also re-manufactures gauges and usually has a selection in stock.
I have a link to Reiner's latest price list on my web site
here. Part numbers ending in an 'R' are re-manufactured, and in a 'Z' are reproduction. Links to two other good sources are also there - Erik Potze (lots of stainless reproduction fittings) and Classic Suzuki Parts NL.
Enjoy !