TMskillerTM made an excellent model for mounting a nozzle brush to the Y-Axis carriage of a Neptune 3 Pro. Was originally only on GitHub.
Their files are here:
https://www.printables.com/model/1284006-neptune-3-pro-nozzle-brush-mount/files
FYI - The easiest way that I found to get to the Y-Axis V-Wheel screws was to remove the tensioner off of the front and slide the whole carriage off of the rail.
The user re-uploaded this model. The user is not the original author of the model.