Hi,
It's not the tow bar that's expensive, it's the dedicated wiring harness - and don't even think of going cheap with the wiring - it interacts with many of the car's systems.
You should have a wide choice from the major European makers like Bosal, Brink, Westfalia, etc., and home produced bars from Witter and Towsure.
The type approval process means that the after market bars will be dimensionally equivalent to the Ford tow bar (which will probably be from Bosal, Brink or Westfalia anyway), but there will be a difference in quality - primarily in surface coating, rust prevention, etc., between the cheapest and most expensive bars.
Robert