software-properties-gtk make sure the universe repository is checked (alternatively you can check
/etc/apt/sources.list to verify you have the universe repositories enabled). After that run
sudo apt-get update.
You can verify the package is there with
apt-cache policy reaver, which should give output like,
500 http://us.archive.ubuntu.com/ubuntu/ raring/universe amd64 Packages
showing you that the universe repository is now available. Now you should simply be able
sudo apt-get install reaver.
Otherwise it could be that this time you installed a version older than 12.10 (perhaps 12.04?). Looking at the launchpad page, I only see builds for 12.10 and later: https://launchpad.net/ubuntu/+source/reaver