When you order a new combine in section 22 order code SB perforated 18' unload auger $148 list. Order code SD for 21' perforated auger $739 list price. This is the cheapest way to get the option. To add it thru parts is much more expensive.
Sorry, but i forgot to mention im in australia - price books here are a little different to the u.s.a one. Will just have to wait until Case IH bring out a productivity / upgrade catalouge for the new series i guess.