I have never seen a "cover" for the fuel tank sending unit, 311 919 051
We just put the frunk compartment carpet it over it and call it a day.
For the hinge openings in the frunk, some people use a piece of vinyl baseboard trim material or a piece of black rubber stair tread cut to size.
But if you want to use brushes then a door bottom sweep should do the trick:
https://www.amazon.com/Pemko-B...4682973314&psc=1
Just cut four pieces to fit the opening.