no idea, but i did something similar a couple years ago. i took a regular 2 point sling, and wove one end of it through the molle on the back of my plate carrier and through the shoulder padding to let the other end hang in the front. i use the end in front like a single point sling, which has a very solid mount, but there are no loops around my neck or arms so it's quite versatile. it looks like that diagram has it attached to the belt in back, which would do about the same thing.
i'd recommend making your own if you don't find what you like
