I'm not sure, seems a quick search did not show much. However, that being said, I'm sure there are similar mattress made in your fine country. The key is knowing how to shop for them. Most people I have met want to short circuit the process, which will end up disappointing you.

You seem to have a base line for what you want, and that is good. Search your local area and find a few good stores that sell a variety of brands. Keep in mind, even if you find the exact same mattress model in Australia, it may not be the same as the one you slept on in the States. Once you have your list, schedule a day when you can spend some time at each store. Approach the sales person and describe the feel of the bed you liked here, maybe even asking them if it is available there. Listen to their suggestions. When you lay on a mattress, make sure you don't pop right back up, spend a minimum of 15 minutes in your typical sleep positions on the mattress. Evaluate the feel, and communicate that with the sales person. You probably won't be able to experience all mattresses on display, and should probably limit your test lays to 4 mattresses per store. Repeat this at 2 or 3 other stores. Once you have found a mattress that feels similar, inquire as to the coil count, the topper foams, in other words start judging the quality.

Once you have it narrowed down to the best fit for you, check on return privileges so that if it doesn't work for you, you can return it. Spend more time on the mattress before completing the sale.

Give any new mattress at least a week and preferably 2 weeks for your body to adjust to it. Our backs need the time to either reject it or start to heal.

Good Luck on finding a similar mattress, or perhaps have one shipped to you, but that might be pricey. At any rate, hope this helps!

Sleep Well!