Looking for Replacement Pivot Bars

I'm looking for replacement pivot bars for my double-hung vinyl replacement windows. I've attached a picture of the pivot bar in the window and the pivot shoe it goes into, for reference. This pivot bar appears to flare a bit before it goes into the window. Unfortunately, I don't have better pictures because the hardware is so old and fragile I'm afraid to take the window out to get a closer look because it might break and then I won't be able to get my window back in. The pivot bar is close to an inch wide where it enters the window and they are metal. Thanks for any info you can provide.

Thanks so much for your reply. I did remove the window to see if I could remove the pivot bar but my window doesn't appear to have any screws on the bottom of it. It has two on the side which I'm guessing holds the frame together and it has two screws on the back side of the bottom frame but I don't know what their function is. Do you have any additional advice on how to remove the pivot bar? I'm attaching a couple of pictures of the screws that are located on the lower frame. The window I am trying to fix is an upper window. Thank you again.