Without a package manager you can download source code. At the website you posted choose "Source Code" and then take the generic one: "Generic Linux (Architecture Independent), Compressed TAR Archive". Now you have to compile the source code. There are plenty of guides how to compile mysql manually.
Another option would be to download the Debian package from the list and unpack it manually:
ar x package.deb
tar xzf data.tar.gz
Then you find the binaries in the folder you unpacked the data.tar.gz.
But be aware, it is a pain, because you have to do this with all the libraries needed by mysql, too