You could write them down on a sheet of paper and carry them with you. That is very secure, but possibly a little inconvenient.

Keeping them unencrypted on a google sheet or word doc in the cloud that you call up as required will be very simple but shockingly insecure. Like hanging them on a public notice board if you are ever going to access the them through a hotel or coffee shop wifi.

Putting all your sensitive material in one place with a simple password would be like putting all your money in a box on your front porch secured only by a simple $3 cycle lock. If you thought of it that way you just would not do it.

There are a variety of options out there, you have to choose what level of security you want.

As explained above, I think the $12 per year "lock" is a good balance of cost for convenience and security across all my devices for all my sensitive data. You may be content with the $3 cycle lock but I seriously caution against just keeping them in an unencrypted document in the cloud.