i have 2 of those aluminum arms that come with the plane, one from a 30% that i had a while back, i didnt use it this time, got the swb offset arm and i like it, there is a round servo horn glued and screwed on the original one if you want it you can take it apart if the horn doesnt work with your servo,
www.acehobby.com sells the planes now, not sure if they sell parts like that, maybe an entire rudder pull pull set up even, pm me if you want the one i have, we can work something out, i have no plans to use either one of the 2 i have