The park is in the New Colvin district
It's below the airport.
It's the STAG 'van' that has a mounted minigun on top. Enter one and it will also say NForcer in the right bottom corner.
The condor theft mission spawns STAG's. Get your notoriety up there and STAGs should arrive with the NForcer. If you can't see the Condor theft in your list, complete a few more thefts. (You should be able to start this theft mission before the Nforcer mission.)