wrong forum ("pharmaceuticals") most people probably extract it from plant sources... sometimes chemists can synthesize it from indole or tryptamine... occasionally a well-supplied dealer will offer it to select clientele... (and it is often a part of the jungle brew ayahuasca or yage...) remember, in most countries purified dmt is very illegal...
from what i hear dmt is pretty damn hard to get and i only know a few people who have gotten thier lucky hands on it.