Question about Flashlight and First Person view

I’m currently working on a Horror Game with a friend of mine and would need a realistic looking Flashlight in FirstPerson mode.

The Arm, Hand and Flashlight should be visible on the HMD the whole time, BUT i would also like to see the rest of the body when looking down (just like in real life), and here is where i have Problems:

What i already tried was:

-I tried to let the leftarm bone rotate on the X-Axis with the camera X-Axis rotation. I made it work, but it looks extremely off, and with a realistic arm position for holding a Flashlight it would more spin from left to right instead up and down.

-I also thought about a seperate pair of arms for my character thats locked to the Camera HMD, but i cant see how that will work when im looking into a mirror or something like this (maybe im just overlooking something here)

Does anyone know whats the easiest and best way to implement a System like this?

(Cant provide Screenshots right now, since im currently not at home. If they are needed i can provide them later)

Looking forward to your answer. Cant wait to proceed working on this.