I am so sorry that you are having to make such wrenching decisions. I am not aware of any specific places that will legally help. We have had many such threads about this...if you do an advanced search on this subject...put in the subject assisted suicide, the forum...survivors of suicide...alffe..and you will see them. If you can't I will bump them up.
In spite of the fact that our only son, a healthy 31 yr old man killed himself with a gun over twenty years ago, I do believe in choices for end of live when all quality is gone. Please know that you are never alone.