Made the rounds of my local stores and found that AutoZone has started carrying a wiper that will work for the rear of the iM.
It is their house brand, but seems to work well. Time will tell how long it lasts.
It has two connectors to pick from, ours uses the "b" version. To remove the wiper, just lift the arm up, and start rotating the blade - when it gets to the point it stops moving freely, pull a little more and it will pop off.
Put the "b" connector on the arm, then snap the blade onto it and you are done.