I've tried all the big ones (Times, Georgia, etc.) and am still having trouble with the "a" and "i". Can anyone assist? Thank you!

You can use the techniques explained in this video: 
https://typography.guru/video/how-to-find-fonts-that-include-specific-characters-r124/

 

You will need to be able to have the characters in the clipboard. So here is the properly encoded string:
Nāda Paśyantī
While those characters aren’t in the 8-bit core set of Western Latin fonts, they are also not rare and are certainly in most system fonts. 

 

Thank you!