NEW Voices for text-to-speech_Captivate 2017

I am creating an eLearning with a narration voice. Unfortunately, the default and free voices you have for Captivate 2017 (David, Zira, Bridget, Chloe, James, Julie, Paul, etc) are not good enough for my audience. Could you let me know where I can purchase voices and install them? The text-to-speech software is an alternative but I believe it’ll better to embed the voice in Captivate and manage it from there. Joe Bavao