The first note is:
Acacia Floribunda is quite active, at around 0.3-0.4%, and is very common along the east coast, even planted in Suburban areas and very commonly in gardens. The good news is you can just take phyllodes (the leaves) from the tree, without harming it. The other most common tree, Obtusifolia is not quite so good for taking phyllodes. The results are often going to be sticky, not so active or you won't get anything from it. And you can't make a brew from it. From all reports Floribunda is a reliable and consistent source of DMT which is the most common source on the east coast.
The second note is:
If you are in WA, you can also take Acacia Acuminata phyllodes, which can contain up to 1.5% DMT. Again, you are not hurting the tree this way and can sustainably harvest it.
Friends also say if you go to any tip in WA, you can find plenty of Acuminata material which people are throwing away, from pruned tress in their backyards and so on.