I built my overhead mount from a couple of 1/2" threaded pipes and fittings. This is relatively cheap and you can build it to exactly the size you want it. Thanks to the threaded pipes you can add more pipes to increase the size.

This is a collection of accessories for the overhead mount. The covers should be printed in TPU and are added to the feet of the stand so it does not scratch the floor. I had to print them with a slightly thicker wall to compensate for the thickness of the "T" fitting.

For the cam mount I used M4 screws (preferably with hex head) and wing nuts on the other side - this allows you to quickly adjust the angle of your cam. The 1/4" cam screw I "borrowed" from my tripod, but you can print your own or get one on amazon. The cam mount is pretty sturdy and you can print it from PLA.

Since most of the time I have a light attached to the cameras hot shoe, I decided to not go with the 3D printed screw and use metal instead.

The cam mount can be adjusted to your liking - especially the width you can adjust in such a way, that you can still access the door for battery and SD card. The attached version will fit the Panasonic Lumix G70.

I had this setup now up and running for a couple of days and it was working flawlessly.