Tilt out window tabs?

These are pictures of windows in my home, which need the tabs pictured in the first two photos. They keep the windows from tilting in, when they are raised. When the window is down and latched, it stays in place. I can't find any manufacturer label or model numbers anywhere on these windows. I have owned this place for 27 years, and I'm guessing they had been installed long before I bought this home. They are made of a metal frame, possibly aluminum? The plastic tabs are on the upper corners of the window that slides up and down. Any ideas as to where i can find these tabs, or how to repair these windows? Or just an identification of these would help me in researching a solution.
Thanks, Ed