I've always used a Dixon locking connection, they have a little locking ring on the back. Most good hydraulic shops would have them or access to them.
https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FbJ0bMkzX0BY%2Fmqdefault.jpg&imgrefurl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DbJ0bMkzX0BY&tbnid=3K8Qk5Qr23mCbM&vet=12ahUKEwjo09WC5v76AhWELTQIHZhCBcoQMygXegUIARD3Aw..i&docid=eWQJlXXEfoh6vM&w=320&h=180&q=dixon%20quick%20connect%20air%20fittings&ved=2ahUKEwjo09WC5v76AhWELTQIHZhCBcoQMygXegUIARD3Aw
