I just looked up servo extension on ebay about 6 months ago and found a place in China that sold me 50 500mm (20 inch) Futaba extensions for about $13 shipped. It took a while to get them but they seem to work fine. Unfortunately they don't seem to be selling anything on ebay anymore but doing the search just now on "servo extension 500mm" returned 100 hits. Good look and good bargain hunting.