My strap release button broke and I was out of warranty, so i remade it, using the top half from the official CAD model and the bottom half as an approximation from the pieces I could find.

If you've lost the original springs, you gotta find some for your own - I just opened a ball point pen and stole the spring from there. Stronger springs = stronger string grip.

Simply place the springs on the little pins on the controller hole, then align them with the cavities in the 3d printed button, and click it down. The hooks on the sides should latch on and the button should work.