In k-Wave MATLAB Toolbox - Legacy Versions (link : http://www.k-wave.org/downloadprevious.php), the download link given for Version 1.3 (Download: k-Wave MATLAB toolbox (7.1 MB zip file)) is the same one as for the Version 1.2.1 : http://www.k-wave.org/getfile.php?id=10.
I was able to download the Version 1.3 by manually changing the link as : http://www.k-wave.org/getfile.php?id=11