After a search here I realized that there was no RJ45 cable protector model on thingverse!
So I used a step file from a grabcad connector & re-modeled (SW) the rear section, with a snapfit function and an open top, just to make sure you have access to the arm.
Print (100 or 80% filled), place on the cable, crimp your RJ45 connector & click it on.
Optional: use some silicone glue to secure the cable on it's place within the protector.
Idea's, suggestion or remarks.. please feel free to add.
Update 29/12/2015: V2 has a larger latch arm opening.
Reason for update: in some cases when you push the latch completely down, it stayed stuck.