Wiper arm mounting lug

I had to remove the wiper arm from the windshield recently and as it frequently happens the old rusted mounting broke. So, I was faced with finding a replacement for this part:

I took a few searches, but finally found this company that has all the parts for the wipers on a typical GB:

Mill Supply (www.millsupply.com)

So that part is a "knurled driver" and mine was a 5/16 inch. Shipping cost more than the part so I bought a few.

They also have the pantograph arms, blades, and mounting plates, so if you need those Mill Supply is a good source.