Maybe a remote signer is what you’re looking for?

The idea being that your business nsec would be only be on one phone or computer, then you would authorize it to sign events coming from other apps and devices.

The spec is nip-46: https://nips.nostr.com/46

Remote signers that come to mind would be:

(Android) Amber by nostr:npub1w4uswmv6lu9yel005l3qgheysmr7tk9uvwluddznju3nuxalevvs2d0jr5 : https://github.com/greenart7c3/Amber/releases

(Web) Nsec.app by nostr:npub1xdtducdnjerex88gkg2qk2atsdlqsyxqaag4h05jmcpyspqt30wscmntxy : https://nsec.app

(Server) nsecbunker by nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft : https://nsecbunker.com