I think
'sourcing illegal substances' is not allowed on the nexus...
There is much information
here that will allow you to get some plant material you can extract dmt from, using a
tek of your liking. Mimosa Hostilis Root Bark (MHRB) is pretty popular, as you can do a straight to base (STB, A/B means Acid/Base) extraction on it, but there are many more plants. You can buy those legally. But even discussing 'from who' is not allowed. Only sourcing live plants is allowed, that you can plant and harvest later.
Buying dmt is illegal in most countries, people who are in it for the money cannot be trusted. Either find a friend who uses it, and smoke together for free, or extract it yourself. If you buy it, anything can be in it. If you make it yourself: you know its good.
Safe travels!