CR, some others have installed an air tank in their rear door (JollyRogerVXer comes to mind) since they aren't using the space to store the standard spare tire any more.

Jay Dunford (former VX owner and current FJ owner) has a nice compressor set up on his FJ so maybe he'll chime in here. I "borrowed" some air from him during Moab and his set up filled my tires faster than any gas station compressor ever has. I'm trying to find room in the VX somewhere to do something similar.