Hi,
Believe it or not i got it in Woodies.. Also any of the door stores will have them... just to clarify a bit more what i did is built outside frame out off 4x2, thats two wall and ceiling. Like three sides of a box.. Then i added another 4x2 that the rails would hang from and i built the 34mm studs inside of on either side of the door rail. The hung the doors and slabbed the entire structure. As for sound no i have no issues at all... I can hear no additional noise at all, i used solid doors and there is a few mill each side of the door left in the wall and once they butt up together there is a good seal as the door is actually inside the wall on all sides bar at the floor as is standard.