Storm window slide bolt/latch

I'm not sure if your latch is available these days. The problem is that the spring you show in your photos attaches to the back of the latch, while the spring attaches to the bottom of latches like our 91-054, and pretty much most of the latches we carry. Did you try a hardware store or a glass shop in your area who repair storm sashes? They might have some old stock lying around you can adapt for use.