Where can i go for instramental versions of song tracks from stage musicals?

Hi, i am new and have been practising songs for my college course to sing with just backing music (or whatever its called). I have found songs with people singing but none with just the music. I need to get the instamental version of cry for me from the jersey boys stage musical but i cannot find it. I posted another question before but called it backing track which was not right. Please can someone help me?