VLSub on the Videolan addons page was recently updated, with new search options.
How to install lua scripts in vlc:
Windows (all users): %ProgramFiles%\VideoLAN\VLC\lua\extensions.
Linux (current user): ~/.local/share/vlc/lua/extensions/.
Mac OS X (all users): /Applications/VLC.app/Contents/MacOS/share/lua/extensions/
But it will not work with VLC 2.1.x. for the moment, so one must use previous versions of VLC.
There is an alternate solution, which works with latest VLC: Subtitle Downloader. On addons.videolan.org there is an older version of the plugin - but that was modified and is rather well supported on thePanz blog, downloadable from GitHub here - with the downside that it works in Windows and Linux, but not Mac. The lua file is to be put in the same folder as above.