I had that same problem finding wiper arms for my 05 Monaco. I know, different MH, but this is what I found out. On the wiper motor was a label with a serial no. and model no. the number was of the entire wiper system
Not just the motor. (Linkage, arms and all) Clompany name on lable was Diesel Tecknoledgy s Greensduro NC. They refered me to Wiper Tecknoledgy, the manufacture, that they had sold off. Also same town. I got both arms, 30 inch blades and some other parts at a very reasonable price.
I hope this is of some help.