Camera mounting insert for standard existing gang boxes?

I have a client who wants about 10 cameras installed around his new house and I need to find an insert that I can attach into the pre-existing gang box holes that the construction crew already cut and installed. Its a standard 4" x 2" gang box.

The problem is, the camera is just a hair too small to cover the entire hole by itself, so we need something in place to fill in the cracks that looks nice.

I basically want to know if there is an insert / mount / something, that I can attach to the gang boxes, then attach the camera to that.

Kind of like the Arlington Cam-Box Kit that has a nice looking fitting around the base of the camera, and that can simply slide/screw the camera on to it.

Anything like this exist?

Thanks!

UPDATE:

This is almost exactly what I am looking for, however this is for a DOUBLE Gang box.. Does anyone know of any like this for a single?

Link : https://www.ptzpros.com/adaptor-plate-for-large-ptz-cameras-to-double-gang-electrical-box.html

I hope the gang boxes are not grounded, ground loops can make trouble. You can also buy a low cost round flat plastic pads used as door knob protectors for walls, they are just large enough to cover the box and they are thin so you can drill holes in them. They come in many colors and are less than 1$ each. Buy them at any hardware store.