nLyrics failed to find lyrics for XXX:
Internet
Use Google, Yahoo or even Live.com to search the LRC file of XXX.
Microsoft Windows
Get a Windows environment and try the following softwares to find the lyrics for you and copy the LRC file back to your Mac: TTPlayer, miniLyrics, Lyricist or whatever.
Yourself
Create it by your self. Please refer to the LRC file format and make sure the created LRC is valid. nLyrics will provide you a convenient tool to creat LRC file in the future, keep supporting her!
Giving up
Which will cost you nothing.