There are only 10 Cop Upgrades. So you have to reach rank 10 to unlock all Upgrades. You unlock Cop Upgrades by completing Cop related missions. These missions are slightly different than the Traids. In Cop missions you start out with maximum points, all three triangles fully shaded. During the mission if you destroy private property, steal vehicles or run over pedestrians, you will start to lose points. You will probably reach Cop level 10 before you complete all Cop missions.
If you do not reach level 10, you can replay any Cop mission. You may replay mission by pressing > Social Hub > Missions.