This is exactly what I thought i'd be doing...bunch of emails out yesterday and one to Murray Park...they have that 73 sitting in the weeds...not sure if they pick at it or sell whole...maybe they have another idler arm to save.Rare Parts does NOT have one on the shelf.
I too did not want to cripple my car. I called Murray Parks and bought a used bad one for $125. I sent that one to Rare Parts and for $292.50 + shipping I received back a new rebuilt idler arm; so all said and done I'm in it just under $450. Its what you do when you love your Imperial.
I haven't swapped it out yet as I'm on a job in Massachusetts but when I get home, it'll be the first thing on my list; which is at the bottom my wife's list...