There are several YouTube videos out there that show you exactly how to build these and you can put them in any container or box you want. I use pill bottles as they are small, free and are easy to work with.
I use the electroscopes by deploying them around a location I am investigating and let them sit and stabilize. This is critical! They need to stabilize because if you touch one, it will cause a static charge to be transferred to the device. By placing them in a location away from people, they will discharge and return to normal operation. These simple electroscopes do not really indicate anything other than a change in the electrostatic field in a location, but imagine having a row of ten of them in a hallway where people report hearing footsteps. Let’s say you have a DVR and audio recorders running in the hallway, and no one is physically present in the hallway, but during the review of the video and audio evidence, you hear footsteps, and on video, you see the lights going out one by one! That would be pretty amazing, as now you have documented a change in the local electrostatic field at the same time footsteps were heard in a reportedly haunted location.
So, you can see the value of simple instruments that measure changes in the environment and provide the investigator a visual indication, especially one that can be caught on video with a time stamp. But with any piece of equipment, you have to understand how it works, what the false readings look like, and never declare unknowns as paranormal… they are just unknowns!
Bottom line: stop wasting money buying over-priced ghost hunting gear and build some simple circuits to use in your investigations!