This video is specifically for DS dolls, but you might be able to adapt this 5 minute project to your needs.
Standard eyebolt ring is M6 (6mm / 0.24") and supports 140lbs. Search ebay for "M6 Eye Bolt" and you can find one for cheap there. This screws into the neck rod of the doll.
The mounting hook can be pretty much anything you have around, I chose one that has a weight capacity of 70lbs, which should cover the majority of dolls out there.
Total cost: under $10
doll hanging system
diy sex doll