I was hesitating about posting that one and ultimately, it is up to him as you are powerless over his addiction.
I think NA has it too but Alcoholic Anonymous has a program which work with inmates. There are meetings in a lot of prisons where AA members come weekly from the outside to share their experience, strenghts and hopes.
There is also a program where inmates are paired up with a sponsor/pen pal (of the same sex of course) who helps them work through the steps. Recently the Grapevine had an issue about people finding sobriety in prison.
AA has also a program to help prisoners who just got released.
Obviously he is not ready right now but if he wants to change and get sober, there is help even in prison and it is free.
The committee which facilitates that is called Hospital and Institution.
There is always a glimmer of hope.
Be kind to yourself
Hugs