I'm pretty sure if you put a file on s3, make it public, it will be accessible for quite a while, with no cost (if it's just text like you're describing). I have an aws account that has the html/js stored in s3 for a static website i created, I haven't paid a bill in years on it, and the site is still running today.

I don't expect it to last 100 years though, they may very well change their free policies a year from now, hell, i don't know if AWS or even Amazon will be around 100 years from now.