You need 4 m5 screws and t nuts and some m3 screws and heat inserts. And optionally you can use a linear rod in the hole on the top of the bracket for rigidity. https://github.com/JDD3D/Rook-2020-Z-Linear-Rail-Mod
Z idler adjusted by https://www.printables.com/@BootStrap
The author marked this model as their own original creation.