Broken part needing replacement

Two of these photos are of the same window. It is difficult to describe, but this is a double hung window with a latch which can be removed, so that the window can be tilted inwards, into the house for cleaning of the outside of the window. When putting the window back in place, there are two white plastic pieces that protrude from the window and key into the vertical rail in the window frame and which keep the window in the rail. The little white plastic pieces, above the screw in the photos, have broken, meaning the window won't stay in place. It is meant to retract on a spring, but because they are broken, the windows won't open safely and have to remain closed with the main window latch on top of the window. Any help would be appreciated in identifying what needs to be replaced. Third photo is of a window where the triangular piece is not broken.