Mine are stamped on stainless steel washers. You can get a letters and numbers punch set for $20 and enough washers to make backups for $10.

Your seed phrase is protected from geomagnetic storms. They do not influence paper

If there is a Carrington level event, protecting your wallet won’t matter. Money won’t matter. The entire world will be set back to pre-industrial era tech, as in no tech. Even if your wallet survived, the systems behind it wouldn’t. And if those systems did survive, digital money as a concept dang sure wouldn’t. We would go back to a barter system for many many years.

Worrying about your money, digital or otherwise if there is a massive solar flare is about as useful as worrying about it if there’s a full fledged world war (nuclear or otherwise). Your 10s, or 1000s, or even millions of dollars don’t matter anymore. You’re either dead, on the way to it, or in a world where the concept of money itself no longer exists.