Window Replacement Part

Hello! We cannot idenify the brand of our windows. I assume they were an affordable option and would guess they are at least 20 years old, probably older. I don't know what to call the peice that we need, window sash? It mounts along the top of the widow. You can see the stamp on the picture provided and also a picture of the whole assembly. The entire assemby pictured, measures 19 1/4 inches long by 1/2 tall and 1/2 inch wide. We would need at least couple pairs. Please let me know if you have anything or leads on where I might find them. Thanks!