Best I could do is drill it through and tap the left side, so you would have to plug the right side. I would do one for you no charge.
If it isn't leaking with the larger carrier, then you were definitely using one that was too tight. You always want to make sure you are using the largest
First thing to do when you aquire any new gun/mag is to clean the entire valve and gun. Replace any suspect orings.
When the marker is