You can find the Prototype Medic Power Armor in Old Olney in the northeast section of the map. The area is swarming with Death Claws. Set the difficulty to "Very Easy", and go there. On the southern-most street of the town is a grate on the sidewalk. Step on it, and it should open out from underneath you, effectively forcing you to go through the sewers. Fight your way through the sewers. Eventually you will find a ladder to your left. Keep going forward to find a Brotherhood of Steel Initiate. She will be wearing the armor. The armor talks and will inject you with Med-X when your limbs are crippled. It is as good, if not better, than Tesla Armor, but does not come with a helmet.