Earth point for front indicator 411 series 3 4 5 6

[Xseries]

Having had my bumpers re-chromed I have discovered that after replacing them on the car the front indicators no longer work. I suspected an earthing issue.

Connect a lead to the earthing point on the Lucas indicators (L787) and making contact with the side repeater screw makes the circuit and works the front indicator. However, I now need to find a convenient point for the other end of the lead. I had hoped the bumper bolt might work as a ground - but no such luck.

Does anyone have any knowledge as to where one might connect an earth lead to a useful ground around the front headlight area...?