The only way is to get a pole with the same diameter and same thread pitch to replace this. This extends the moment arm the weight of the monitors have, and will significantly reduce its weight capacity. What you can do is add a reinforcement plate and ensure you keep the monitors as close to the pole as possible.
Also, I have the triple monitor mount with another single monitor mount on the bar for a 4 monitor mount setup with a reinforcement plate. I am able to mount my 4k monitor overhead with some good height. I could even put it higher if I wanted to, but wanted the top monitor to not be so high up. Not sure if the bar is just longer on this mount or something, but the bar with my single monitor mount I did not use was certainly shorter than the triple monitor mount.