I say find a nice mountain that doesn't move and put the camera on it instead
Seriously, though- all you need is two guys, each with a rifle scope on a tripod. One on his back looking up at the helicopter, and one in the best lateral position you can find (is there a building in the vicinity? If not, then he has to position as far away as practical and utilize a diagonal view for altitude).
Give each one a radio.
The guy on his back is call sign "position", the guy in the lateral position is call sign "altitude". They could keep you in a 50 ft box with a little bit of practice. Just have them give you vectors.
Ex: "Position- correct left" "or Altitude- correct down"
Don't drink coffee beforehand, and try to stay relaxed.
