Young1 (and Bob
),
Is this what you meant?
Wiper Arm Adapters
If you Google "windshield wiper knurl" or "windshield wiper adapter" you'll find the above and more, such as this one too:
Specialty Power Windows
I know about these because mine broke continuously when the car was first put on the road - yeah, I know, I was driving it in the rain - still do
I keep a spare now, although if I had to find it, well, you know...
Hope this helps,
Tom