big_frahm , If wire not broken, use 2 part epoxy to glue the antenna back together. See 1st link below video showing how to repair antenna.You could also try contacting DJI at the 2nd link below to see if they have a replacement part for you. You can also purchaser a new range extender antenna setup which would replace the factory antenna(3rd link). Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
https://www.youtube.com/watch?v=IyxbZ48wHXs
http://www.dji.com/contact
https://www.youtube.com/watch?v=5UYg45AtqpA