There is a blank nozzle available as part of the Low Angle Nozzle Set (Part Number 233200), which can be inserted into the PGP-ADJ to shut off the flow of water.
Remember the riser will still pop up as if the rotor was still going to water so be sure not to use the plug as a permanent alternative to capping the head off properly. These nozzles should be used as temporary plugs to help flush lateral lines and assisting in maintenance procedures. The blank nozzle will need to be taken out if the system is to be winterized. Capping or removing a sprinkler must be done differently if the area you live in requires winterization.
The PGJ does not have a blank nozzle to shut off flow to one rotor. If you want to shut off one PGJ rotor, you would need to cap off the sprinkler head using a 1/2" plug/cap. These PVC parts can be found at any local hardware outlet.
The I-20 has a Flo-Stop control where the flow can be shut off at the rotor. The Flo-Stop is the hole in the center of rubber cover. When the I-20 is operating, insert the Hunter adjustment tool and turn clockwise until water flow stops.