Google provides you access to one-time codes, if you wish.

I thought you were joking.

Sign in using backup codes: https://support.google.com/accounts/answer/1187538?hl=en

There's a compatible OTP app for nearly every OS. Ideally you'd be running it on a device that isn't the same as the one running your web browser, but you could just install e.g. a Windows OTP app and use that. Better than nothing.

Personally I use a phone, but I also own a TI Chronos programmable watch that has Google OTP support.

The algorithm is fairly straightforward and does not require internet connectivity (through mathematical magic).

Interesting, I hadn't come across that watch before. How do you like it? Can you compare it to something like a Pebble: size, battery life, screen quality, etc?