black piece for casement window

I have Weather Shield casement windows and am looking for a part. The attached photos are from the right window of a double unit, the left window is the problem. The part that is broken keeps the window from pushing out when you open it, it's the black plastic part, it glides in a small track that let's the window open 90 ° to the frame. Photos are attached. Don't know it they are same for left & right side or are hand specific.