If I understand the comment above correctly, one can carry an I94 too and those you can just print on the website [1]

I'm guessing there's no size requirements? If so it might be a good idea to just print four on an A4, and have one folded in your wallet, one tucked in your bag-pack, one in the car, etc.

[1]: https://i94.cbp.dhs.gov/search/recent-search