The site does include a way to use a throwaway key and IIRC it was there last night too.

    ssh-keygen -t ed25519 -f ~/.ssh/late_throwaway && ssh -o IdentitiesOnly=yes -i ~/.ssh/late_throwaway late.sh

Based on what another user said, you might want to modify the above command to use throwawayUsername@late.sh instead if you are going the throwaway route to be more certain you aren't leaking your OS username.