Pella screen door latch

It's tough to be sure what you have when the part is broken, but it does remind me of our 85-020A. Look over this part and see if it might be what you're looking for.

That keeper looks very similar to the 85-020A mentioned in this thread. Have you looked at this part yet? If not, your next step should be to review its specs to verify that it is the same size and design as the original piece. 

Alternate view of 85-020A