Baseus camera detector
Baseus camera detector is a simple gadget that can be used to find hidden pinhole-type cameras. The device has 4 bright red LEDs and a red filter through which you will be looking. The concept is simple and uses reflections from camera lens elements to detect otherwise hidden cameras. There will be reflections from shiny elements and some bigger lenses (or those without coatings?) may not reflect the light as expected.
There are multiple devices using this device, and you can find them in various stores. I got this Baseus one from Aliexpress.
The detection isn't very apparent, but it is there, but it may depend on the lens. You will likely also want a dim environment to better see them.