HOG D1 cold water 1st stage regulator O-ring question

[blue steal]

I have the HOG regulator set up. It has been served me well for many dives in both cold and warm water. Gotta love em.
What I am looking for is the O-ring that fits inside of the DIN "lockdown screw" that secures the hand wheel for DIN 1st stage.
The outside O-ring that interfaces with the tank valve (112) is okay, but the O-ring on the inside is leaking and none of my other O-rings fit.
Have tried sizes 011 & 012 (to small), and the 112 is to thick and big.
Any suggestions?
Thanks

 

[blue steal]

After much investigation and reading service manuals and the help of the good folks at Dive Gear Express I was able to find out, (and order), the size of the O-ring: The inside of the lockdown screw on the DIN is a 013.