I have gone through your question. There are many formula feeds in the market which help in supplementing breast milk. First are the most basic ones like Lactogen 1 and others are little premium ones like NAN PRO1 or Enfamil
with added DHA
and extra supplements. I would suggest if cost is not a problem you can go for the premium ones.
Secondly i would strongly recommend that mother should continue breast feeding regularly and formula feed to be used as supplement only.
Thirdly for mother to have more milk it is advisable that she drinks lots of water[2.5 L/day] and have nutritious food.
Hoping i was able to help you