I bought mine several years ago from Alex at ATP. and was very happy. http://shop.aviationtechproducts.com
My buddy bought his from Stien and they made him a package deal on the AP
and the harness that was pretty nice.
Good Luck.
You might consider buying mine---I just yesterday posted an ad(post) offering it for sale. I just removed it from my 601XLB because don't use it, and besides that need the money to go towards the panel in my next project. Its about 2 1/2 yrs old, has recent updated control unit and both servos. I bought it through Alex new. He said to list it on Vans Airforce classified. I need $2950.00 for it. Call me, Tom @ 816-699-5221.