Post up some pictures of your machine, we love pictures!!
For the wiper motor arm, a picture of your shaft and motor help idientify the make of the wiper motor. This will help to identify yours. Any names on the motor housing??
As a side note many of these machines had wipers similar to what was being used on construction and Ag machinery back in the day. Maybe a savlage yard with old constrution equipment would be a place to check out.
Regards, Kirk