Most of the times only the the arm is missing, if it looks like this:

you probably only need a new arm. That's
parts number 2LE2-1B (all
Edge arms come in black). An Edge arm needs two bushings, but I believe those are included if you order a new one (although you can always order some extra replacement bushings, they're not that expensive and they do wear out eventually). Rich will probably know for sure if you mail him

You can also post pics here if you're not sure.