Jerry Baker wrote:

What I can't figure out how to do
is stick the plastic to the overflow without using glue or silicone
since I want it to be easily removable.

Head down to your local hardware store and pick up a few nylon machine screws
small enough to fit through the slots in your overflow. Drill your new black
plastic in locations that match the slots and run the screws through the plastic
and slots to hold the plastic panels in place.

George Patterson
All successes in conservation are temporary. All defeats are permanent.