Car wash broke the rear wiper - looking for part number

[998M]

Because the truck is black and I live in crappy Wisconsin, I wash it every other day. The other day one of the brushes caught it wrong and tore off the rear wiper. It looks like I will need to replace the wiper arm and the part that the arm attaches to. The wash has agreed to pay for it but I am having trouble ordering it.

www.realoem.com is down for now. So I went to www.bavauto.com

I found the p/n for the rear wiper arm (61 627 161 028) but have no idea what the p/n or even what the part that the arm connects to is called.
Any help?
Thanks
M