Loctek D7DR Dual Monitor Mount fits for both Curved and Panel 10-34 inch Monitors Gas Spring Monitor Arm Desk Top Mounts LCD Arm (Weighting 8.8-22 lbs)

I could not find anything with the same sturdy build as this mount. It was expensive importing it from the USA, but the additional cost was worth it in my case. I would recommend that if you use it by making a hole in your desk, do add pads between it and the desk to stop it rotating in the hole. If you have a solid desk, this may not be an issue for you, but as my desk top partly hollow box construction I could not tighten the mount beyond a certain amount without breaking the desk.tl;dr - expensive, but worth it.