The Internet Archive come to mind.
Cron does not like dots in the filename of your script. Does it work if it is just “backup” instead of “backup.sh”?
Have a look at the most upvoted comment.
Pull up the string a bit and try again (?)
If you copy the whole URL into the search and wait second it should work for communities your instance did not know about.
btw: you can find communities with this.