Vocodex is included in the FL Studio Producer Edition and higher. If you already own these versions, you do not need a separate download.
There is no longer a completely "free" standalone version of Vocodex for permanent commercial use, as the VST2 version was officially discontinued around 2021. However, you can still access it through the following legitimate channels: il vocodex free download
Most links for "il vocodex free download" lead to: Vocodex is included in the FL Studio Producer