Since the Windows 10 Fall Creators Update, the location changed to:
C:\Users\USERNAME\AppData\Local\Packages\{DIST}\LocalState\rootfs\home\{LINUXUSER}\
Where:
{DIST}
is equal toCanonicalGroupLimited.UbuntuonWindows_79rhkp1fndgsc
{LINUXUSER}
is the user for which you are looking for the .bashrc file
Just for anyone wondering that came here from Google.