Drush on production server without Composer
If you don't want composer in production on your server, you can run the composer commands locally to install Drush, then make sure to push the vendordirectory to the server. Make sure to also commit the composer.json and composer.lock files, so that anyone else working with the codebase can handle composer on their own local machines as well.

In this way you never need composer on the remote production server, but can get drush.