Keychain ones are not made any longer. When Bliz went to the one for the phone, they discontinued the fobs. I saw that being announced so I purchased an extra one for myself. So now I have my original, plus an extra backup one for my own use.
As of 2019, the physical authenticator devices are no longer manufactured and offered by Blizzard Entertainment
Apparently, there is still some discussion going on about all this but from what I understand, there is a way to download the ap to your pc as well. I recall someone saying they use Bluestacks for theirs, but I’m not using that ap so I have not invested much time in research on it.