Corner brackets for screen windows with a number 3 on it

I'm not sure what it is you're looking for. Can we see a picture of the part in question?

Thanks! I recognize this corner. This hasn't been made in a long time, unfortunately, and there is no confirmed substitute. Looking through our records I can see some of my colleagues suggest trying to adapt the 95-187 to the frame, but there is no guarantee that this will work, nor as to what type of adaptation may be necessary. At the end of the day, it may be time for new screens. 

I'm sorry that we couldn't get you a better solution.