I use GPW strings for this use-case. GPW has weaknesses that make them somewhat poor for use as first-line passwords, but they're still really good for passwords that you need to read to someone over the phone.

In my most recent experience with them, the company allowed to be set both the question AND the answer. So, they had to read a random string to me, and I had to read one back. It went quite well, actually.

https://multicians.org/thvv/gpw-js.html