Door lock latch wouldn't retract fully due to a broken spring

I have what I believe it's called an "atrium" door and the lockset that goes with it has a very small backset. As I turn the key or the knob on the inside, the latch would not retract fully half the time. So I removed the lock and opened it up. Inside I saw a spring broken into pieces. I have a matching backdoor with the same lock, so I removed that and looked, and I can see what that spring is supposed to do. I don't see any brand, model marking on the locks. I believe the locks must have come with the doors that way as the holes seem to indicate it was a package. Image: http://i173.photobucket.com/albums/w67/143house/7th/withlockremoved_zps7ce83523.jpg