Where can I get the repositories for old Ubuntu versions?

Your system is End-of-Line (EOL), therefore not officially supported. Unless you have a good reason for sticking with 9.04, upgrade to a newer version. 18.04 is the next long-term supported release for Ubuntu, which will continue to receive updates.

To access old Ubuntu repositories, take a look at http://old-releases.ubuntu.com/.

There is also an official Ubuntu documentation for EOL upgrades

They say you should be able to access your packages by putting the following into /etc/apt/sources.list. Important: Change CODENAME to your distribution's code name, e.g. jaunty.

## EOL upgrade sources.list
# Required
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-security main restricted universe multiverse

# Optional
#deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-backports main restricted universe multiverse

Just run apt-get update and you can use them.