This adapter is exactly what I wanted. I just use the microphone port as my headphones are connected to the TV instead.
It sits snug enough on the bottom of the controller. However even though this one is better built than the other one I had (small box, can't remember brand), I feel it could break just by looking at it funny.
This appears to be the most up market adapter I've come across so far though. The market for this kind of product isn't very big at all. This product is the best in a tiny range of competitor products.