The Aussie heads are becoming more readily available in the US. Tim Meyer Inc. is a great place to get them, you have ALOT of options that you can order them with, and price wise they arent to bad from him. You can also buy the bare head from him i believe if your wanting to keep it a little cheaper and do your own setup. Here is the link.
TMeyer, Inc. - Machine Shop Prices you can only get the Aussie heads from him for the 351M and 400