Zipper

I imported the original STL into Fusion 360 and used it as a pattern to create this one. I wanted the separator to be a full triangle instead of a diamond shape. I also needed to modify the hole a little. I've uploaded the Fusion 360 file so you can make edits as you'd like.

Update 1/18/2018: I've had this on my vest just over a year now. It works like a charm. I've added a slightly better picture of it.