Any ideas where to get a screw for the 3rd brake light on a 2011 Prius? https://image.ibb.co/dG96dJ/Prius_Brake_Light_Screw.jpg
Dealership parts department. There will be a specific part number for that, it's the safest route. That's a metric screw, and what's referred to as a "shoulder bolt": the thickened shoulder is designed to chinch down without crushing delicate plastic.