Pivot shoe broken

Hello,

I'm trying to find a replacement pivot shoe. The part is 2 inches long by 1.25 inches wide, and 9/16 inches thick. The number on the part is 4610.108 and the window was made by Rivco in 2000.

It has an "open" top allowing the window pin to slide in from the top. I'm confused why a number of the pivot shoes on your site appear "closed" from the top.

thanks,
Jim