If the official Xilinx archive no longer serves 2014.4 (which is likely), you cannot legally obtain it elsewhere. In that case, contact your university lab instructor or company's IT archive – they may have a local copy.
Officially supports Windows 7 (64-bit) and specific versions of RHEL and Ubuntu. vivado 2014.4 download
: This is a 1.12 GB update that must be applied to an existing 2014.4 installation. It is primarily required for users targeting UltraScale devices. If the official Xilinx archive no longer serves 2014
Since 2014.4 is not on the main download page, you must use the system. vivado 2014.4 download
Production-ready support for Kintex UltraScale XCKU040 devices.