How do I suppose to heal my arm?

According to Fallout Wiki limbs can be healed with Doctor's Bag or by Doctors them selfs. So far no luck finding Doctor's Bag and the Doctors doesn't have that option, their regular healing seems have no effect on my limbs condition. So few questions here.

1 Where can I get Doctor's Bag?
2 Which Doctor can heal it?
3 What is the skill requirment for Doctor's Bag to be in effect?

If you think there is more I should know, Please add.