Hey there TM11,
I apologize about the late response, thank you for being patient! Were you able to find the answer to your question?? If not, I'd be happy to help out! At the moment, the Chromecast Voice Remote is only compatible with the Chromecast with Google TV. It will not function with any other model of Chromecast.
I hope that answers your question, and if you have any other questions or concerns for me, please let me know.