42mm Alumina's are not available yet. Late 2013 is what I've heard also.
Assuming you're looking at these for a VX-6, check the thread dia and pitch (call Leupold if you have to) of the objective. It might be that the new aluminum flip-ups from Swarovski MIGHT fit. IIRC, Swarovski uses a M44 x .75 thread for their thread in 42mm scopes. I know, it's a shot in the dark.