Windshield wiper mechanism

I have a 1983 733i and I am trying to find the parts to replace my windshield wiper mechanism. It was acting funny and when I opened it up I noticed that one of the arms inside were broken. I can not for the life of me find where to buy a new one online. The closest thing I have found so far is this: http://parts.northwestbmw.com/a/BMW__/43662097__5807517/Single-wiper-parts/61_0894.html

Please let me know if this is what I need.

Thanks!