30+ Traco windows

I just want to replace it, if I knew what it was called I would name it. It appears that there is a groove that this piece slides into. Some of them are shorter than others and that is also why I want to replace, there is left a gap for bugs to get into. I hope you can help me out. I would like to replace the rubber stopper that you see in the picture that kinda holds the screen against the end of the window. It is old and yellowed.