Go to this thread for more information:
https://www.winnieowners.com/forums/...ps-358143.html
I think you are asking about a Trico Plastic Cover, ~ 4 inches long, 1 1/4 wide and snap over the mounting bolt on the wiper arms. Part number AW-RPHC
Call:
Rome Truck parts
800 284 4345
Talk with Kristen or Bill in Parts
* If this is not your cap then ask Rome if they can source it for you.
* And this would be a good time to oil your neglected, articulating wiper arms you don't see. Also you should tighten up any loose bolts in this mechanism.