There's a ton of online sites for it. I used something custom, but the first result on google seems like it would work just fine. https://iancoleman.io/shamir/

I kept a copy of the combined secret... it's the secret key to my password manager. I do have a plain-text document that fully describes the steps to restore my identity, but it's addressed to myself. My goal is to get my own identity back, not to prepare for my own death.