I did find a replacement belt at TSC (96" kevlar v-belt )- although I am not sure if it will work just yet. I spent the day on sunday trying to get the shaft assy's disconnected so I could install. Unforwunately I could not get the vertical shaft disconnected. I removed the 6 5/16 bolts that attach the sickle bar shaft to the bearing.. I need to find an illustration of how the shaft attaches to the pulley. I was concerned about breaking something so I stopped.
BTW - Similar failure - when I hit some tall grass the belt came off the machine. With the new belt - hopefully it will be able to handle this.