running wires through glareshield

[rv8ch]

I expect that I will need to run some wires up to my glare shield - perhaps a HUD one day or at least an AOA - and I know some put their GPS puck there.

Does anyone have a clever way to do this? I've seen a simple plastic or rubber grommet but was thinking about something like some overlapping rubber flaps, or some brushes, or something else. It would allow a tight seal so stuff does not drop down there, and be big enough to pass the cable connector through, and allow for future expansion.

Thanks for any suggestions.