If there is a wire that connnects the AUX Jack to the back of the Radio it would have a part number and could be ordered. I have searched long and hard for that very wire. At College Hills Honda you can search the Honda Parts Catalog in the Honda Fit "Sport" section. Searching I couldn't find a wire to connect the AUX Jack to the Radio. The Honda parts drawings are too hard to see, but I think that the wire going from the Aux Jack to the Radio might be bundled into a much larger wiring harness for the rest of the dashboard since I couldn't find it.
I to have a Base model FIT. I ordered the AUX Jack Part# 39112-SAA-J02ZA from College Hills Honda.
You can add stock looking AUX Jack to your car.
The back of the Jack has 5 connectors. Following the instructions listed above and in other forums, you mostly likey can figure out how to wire this Jack up to the back of the Radio. You would need to run your own wire though. I haven't had time to wire it up yet.