Basically this is only a script that is too basic for save use, but my knowledge and time is too limited to make it much better.
I took it in pieces from other stuff.
You will nee one normal VocalizerTTS folder with one voice in it.
Than you need a second TTS folder for the second voice.
This second folder needs to be renamed to Voc1 or Voc2 - you select the corresponding menu button to "switch" , but you have to know which voice is currently used as the script does not check anything it simply renames the folders.