MP3 Audio CD in a Prius

If you're in the U.S., it should've been made available. it's located in the centre console box between the front seats.

If you're not in the U.S., then you'll have to check with your local dealer. (And soon. Toyota dealers don't keep accessories for cars long after they've been replaced with a new generation. In the U.S., it's typically 2 years after the launch of the new generation).

Yeah I'm not a fan of the MP3 CD tags where it shows the filename rather than the song title. However, I've been using BT Audio and it shows the tags properly.

The newer headunits will allow browsing of the phone or mp3 player connected via BT or USB.