This requires some saving reloading and reverse pickpocketing. Take Eugene as your reward.
Now take some power armor and good repair and reverse pick-pocket it onto one of the rangers. Brick has a fairly low perception so you shouldn't have much trouble. Leave the area and come back. Brick should be wearing the power armor you can then attempt to steal the battle armor.
- reload if your caught pickpocketing.
Fully repaired combat armor may work as well as the ranger battle armor Brick is wearing will probably only have 50% condition remaining when you meet her.