May I ask why? If there's not a high chance that you'll be interrupted, you don't need to put all your points on "can't be cured." If you use SN you can easily be revived by methylene blue, but it doesn't mean that it's not effective so long as you block out 45 minutes of time free of people in vicinity. If you're in the psych ward, how long is your stay? What I did is basically behaved like a model patient in the ward to get released earlier, because all the resources are OUTSIDE of the hospital and trying to do it within the hospital is just putting yourself on hard mode for no reason.
You can look into sodium azide though. It's not painless, but there's no cure for it. It's very easy to obtain within the US. No need to use shady sites or anything.