If you want a manifold that actually works (not like those cheap ebay 'specials' that will need constant attention to fix gasket leaks/porous etc...) ring Harrop Engineering directly: 03 9474 0900. You can order directly from them.

They pour them in batches so you may need to wait a couple of weeks but you might strike it lucky and they'll have a dual plane on the shelf. I haven't bought one from them in over 12 months but I've never had any QC issues with their stuff.