Dash Cam in Grand Scenic III

I'm wondering if somebody here can give me advice regarding the installation of Dash Cam in my Grand Scenic.

To comply with the law I'm planning to install it within 40mm in zone B on the passenger side of the rear view mirror (as mentioned in some other posts in this forum).

I'd like to get 12V to USB converter, but I'm not sure where is the best place to connect it without doing too much (any) damage to the interior ..

There are some wires inside the rear view mirror holder where the light/rain sensor is. Does anyone know if there is a suitable lead I can steal some juice from? I'm not entirely sure how to open it and check without breaking it.

Alternatively I can take the lead down the passenger side pillar to the fuses in glove box, but again I'm not sure now painful and damaging that would be.

I'm sure people here must have done this or something similar. Anyone can give me any pointers?

Thanks a lot

Dash Cam in Grand Scenic III