I looked at a multitude of covers, including the plans, but the one that struck me as elegant was the wrap around cover as it retains the pin and also hides the gap between the two cowls at the intake.
Imitation being the sincerest form of flattery I merged two designs I had seen into what you see.
The covers were made from some 1.5" x .025" spare trim material. The cowl was c/sunk and the covers dimpled for #8 screw - simples.
