Hi Max - the company 'Everbuild' based here in the UK has a global reach, and so their products might be available in Oz - worth a quick search perhaps ?
They manufacture two glues which might be of interest: one is called '502' which is D3 grade (meaning it's an external/water resistant glue, providing it's covered in some way - painted etc). The other is called 'D4' which, as it's name suggests is D4 grade (100% waterproof/boil-proof etc).
I use Everbuild D4 for just about everything - joint construction, as an edge sealant etc.
'best
LJ