This should work. Description: Campagnolo Stepped Gear Ferrule 4mm. It should take 4mm cable which is what the coiled wire gear cable is on old steel bikes. Or you can use modern SHIFT cable and housing which is 4mm. Brake cable housing is 5mm and probably won't fit.
https://www.condorcycles.com/product...d-gear-ferrule These are extremely hard to find. Folks want $10+ each plus shipping on Ebay. This company's price as I write this, is $2.99 each and $5 US shipping. So buy some extras.
