Unless you get a nonlinear junction detector, I'm not sure any other device works as well. I remember seeing a news piece where they pay someone to plant a bunch of cameras, and the reporter tries a bunch of different devices and still misses some.

https://hackaday.com/2017/09/20/spy-tech-nonlinear-junction-...

It would be nice if someone could make them and sell them cheaply. I would buy into that Kickstarter.