As for it not being available to Australian addresses (despite the other three being available), is a bit strange.
Both this pack and the Autobot Clones were originally planned to be sold by Amazon Australia (as domestic stock), but since the Autobot Clones pack didn't show up on the local site I wasn't expecting any of them to... but if this one is coming here as domestic stock, it might be why Amazon America has them blocked to us if they were not allowed to be "competing" with the Australian branch.
Maybe...