That’s a tricky position to be in - you have my sympathy.
Personally, I would very much want to get a backup before trying a rebuild. If the regular backup process isn’t useful to you (because it sends backups somewhere inaccessible) then I’d try somehow to get a database backup using the command line, but I’m not sure exactly how. Maybe pg_dump inside docker?
Or maybe you can use your command line access to redirect backups to the local disk instead of S3.
But in both cases you will need sufficient local disk space.
Edit: crossed in the post with Jay.