Some of the required supplies are available in Australia but I have not heard of a complete kit for a mega tree. Regardless, I would suggest putting together a DIY plan for a mega tree even if you find a kit option. The kit option would not take your specific preferences into account so it would be a good idea to compare it to your ideal mega tree.
There are quite a few forum threads here where members have posted the details of how they built mega trees. I listed a few in this thread: https://auschristmaslighting.com/threads/13452/
There would have been more posted since then too.
