Step 1: The Hitch Mechanism
$18 with shipping
I made some teflon washers to go against the bracket and tightened the backnut against the joint to allow a little slack for y-axis movement of the arm beyond the ball joint movement.

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I love repurposing & recycling!
Here is another resource for parts like the ball joint:
http://www.mcmaster.com
I found some on their that would have cost you less, but you have to watch out for their shipping. Some were made of Stainless Steel (& shielded), and they have one that doesn't need lubrication as well (won't squeak?). Maybe some upgrade possibilities?