To my knowledge, libc6 2.29 is the latest version. And it is available for Ubuntu 19.04 (link).
If you want to install libc6 amd64, open this link to download it, then open the download folder in the terminal and run
sudo dpkg -i libc6_2.29-0ubuntu2_amd64.deb
If you want to install libc6 i386, you can download it from this link, then open the download folder in the terminal and run
sudo dpkg -i libc6_2.29-0ubuntu2_i386.deb
As per now, libc6_2.29 does not exist anymore. However libc6_2.30 and lib6_2.31 are available via this link
(2.31 is the official version for Ubuntu 20.04).
If you want to download a different version than the official one supported by your Ubuntu release (i.e 2.27 for 18.04, 2.30 for Ubuntu 19.10 ...), check this link
Download the version that suits you, then open the download folder and run
sudo dpkg -i <the_file_name>