Peerless Assassin 120 Mini fan replacement / addition?

I'm still using my Ncase M1 classic daily, and want to upgrade my CPU cooler from Noctua U9S to this cooler. I've seen a build that's using one of this, and looks like it's working well! However, I'm a bit concerned, as it seems that TR is using a custom 120 mm fan to reach that 135 mm height. Is there any replacement for that fan? Or probably an upgrade for that fan? Or maybe additional fans can be installed on the sides?