[rickj]

My wipers were skipping removal of water in the middle of the windshield and so determined that the springs were worn. When I removed the arms found that the idle spindle was rusted out and bent. So this began a search for replacement parts; since my coach is a 1999 #538 the search became problematic due to age. After hours of searching and re searching (if one starts a new search other results pop up that otherwise had not been flagged before) and found the replacement parts as follows:
Bosch dual wiper arm assembly 3-398-100-090 HD Truck Bus Dual Arm 730mm; the numbers on these exactly match those stamped on my old arms. 
ebay link- https://www.ebay.com/itm/265775654459?ch...47c6d56d2c

My search for replacement pivot plates ended with American Bus, Part# A422628001.  Link- https://american-bus-inc.com/parts-and-accessories/
I don't have a picture of the pivots plates as they are presently in transit, however included in attachments is the American Bus wiper page parts list.

Finding these parts was a great relief as no custom work needs to be done-just plug and play.