I always had my eye on the compartment under the rear seat which houses the factory bottle jack. This compartment also houses the factory locker compressor and wiring harness. The harness is there on every Gen 2 vehicle regardless of locker fitment.
I bought a air compressor from RKS in Braeside (flows 37.5 ltr/min, ARB = 29.5 ltr/min) for $90, comes with a kit bag and attachments.
I found that the compartment cover is held down by about 12 bolts so took it off and removed the bottle jack and stuff. The compressor fits in perfectly so I'll get another one for the other side, bolt them in, get them wired up to a switch on the dash, plumb them together and have one attachment for an airline. I will have to grind off the jack mount also (spot welded to the floor). Combined flow will be 75 ltr/min (twin tongue is 85 ltr/min, cost $800). All up should be about $250. For $90 per compressor if they last a few years I'll be happy.