Need replacement part for H-R55-44x71

Hello - I've attached a few photos to show the broken part on my window. Trying to identify what this is called and where I can get my hands on a replacement piece.

I do have an in-tact sticker w/the serial number and whatnot, but honestly am not sure any of this information actually identifies the manufacturer of the window and can't locate any other manufacturer names stamped anywhere on the window to contact them directly.

Any help is appreciated!