If you can name me a phone the size of a CC ...

Men can dream, can’t they?

We had these in the 80s:

https://en.wikipedia.org/wiki/Casio_Film_Card_calculators

I don't think it's too wild to expect Linux to run in this form factor, 40 years later.

Especially if you’re not looking for a gui. Just one lean SOC, stuff for power, and 80x100 character display.

There are a bunch of tiny, no-name Android phones with 3” screens.

They’re awful to use but they are very cheap.