You might try this. I can’t vouch for it but the concept seems interesting to me. https://www.punkt.ch/en/products/mp02-4g-mobile-phone/ https://www.punkt.ch/

You might try this. I can’t vouch for it but the concept seems interesting to me. https://www.punkt.ch/en/products/mp02-4g-mobile-phone/ https://www.punkt.ch/en/products/mp02-4g-mobile-phone/ It’s a small candy bar phone but maybe not square enough to fit in your wallet.