Not sure where the phone ariel is on the 4200 , i thought it was integral with the front screen , if its the rear wing ariel your talking about you find one on most volkwagons , exactly the same on my sons 55 plate polo
I had the same problem when some ****** nicked mine. Cost me £65.00 to replace it from Eurospares and half of it's stuck in a drawer at home, as I only needed the screw in bit.