Since Evapotranspiration is ...
Published by Lamyaa Tayseer Negm, Postdoc Research Associate, NC State University
Since Evapotranspiration is normally a major component of the water balance (hydrologic cycle), try to utilize the MODIS ET data.
https://modis.gsfc.nasa.gov/data/dataprod/mod16.php
Maybe it has been highlighted in previous replies. Also, check other forms of available weather data in case any are relevant.
Good Luck