Anyone know the best way to mount monitors to get this setup?(Bad diagram inside)

I'm looking to get my monitors set up like this
I've got two of these holding up the 21:9 and the side portrait monitor. I tried to use an extra arm to mount my third monitor above the 21:9, but the pole doesn't go high enough for clearance.
So I was hoping if someone here knew of any mounts that could accomplish this.
Also to note, I want to avoid any mounts that sit on the desk, I'd like ones that clamp on the edge like the ones I have.