ErGear Single Monitor Arm, Adjustable Desk Gaming Monitor Mount for 13-34″ Screens, Up to 19.8 lbs, Enhanced Stability with Integrated C-Clamp, Upgraded Cable Management, VESA 75x75/100x100mm, Black

This monitor arm from Amazon helped me tremendously. Same issue as you, SI joint and sciatica painso I bought a standing desk two weeks ago, but I still had the same problem with my neck. This monitor mount arm extends high enough for you to look forward or even up most monitor arms are not tall enough for your set up. You can even set up the pole slight offset to the left or right so that you can swing the arm back like 6 inches so the monitor is further away from you. I did this with a 32inch monitor that was too close to my face. Helps not strain my eyes as much. https://a.co/d/09xbud7n