I don't think this can be solved with book recommendations or one-liners. I bet the PM already knows it's unreasonable to ask for 100% quality. The person in question probably comes from the mindset that setting an unachievable bar forces quality; like the line manager that screams when there's a speck of dirt on the floor after a shift.

If you must continue to work with this person then you need to play by their rules. Create a manual test suite that takes about 2 hours to complete. Every time a new issue is found tell the manager that you'll add X tests and increase your test suite. Eventually you'll have a test suite that takes longer to run than the bug fixes. If the manager doesn't like the drop in performance ask them which tests you should pull out.

Unit tests are arbitrary magic to non-developers whereas tests written down on paper are tangible. They can see the document grow in size and they'll start to see their name appear on the document (Added 25 more tests by direction of Joe Manager). Managers can hide from unit tests, they can accuse you of not writing enough unit tests, it's harder for them to hide from physical tests.

It's not fun. Really I'd say find a new job.