Google has officially confirmed the discontinuation of the Chromecast Audio device. A quick glance at Google's online store lists the music-streaming gadget as out of stock, after recently receiving a heavy price cut from US$35 to just US$15. It may be possible to buy the device in some outlets while they still have stock remaining.
https://www.notebookcheck.net/Google-discontinues-Chromecast-Audio.393896.0.html