I replaced mine recently and hit the same problem. My solution was to ring a local Fiat dealer with my VIN number and ask for a price for the cable. When he told me £70ish I laughed and asked for the part number, then spent £26 on ebay.
With hindsight I should have asked which gearbox I have but I only wanted the cable at the time.
Don't trust the "Check if it will fit this vehicle" bit on ebay. I needed the shorter cable but most sellers seemed to think I needed the longer one. Mine is an R reg 1.9td.