Hi Sina
I was in the same predicament as you. Perhaps you have solved this issue now? I am now 22 weeks pregnant and will be going to Vincent Pallotti with a private midwife (I am using BirthOptions) and a back up doctor. My medical aid does not fully cover Vincent Pallotti nor a a midwife+doctor, so I am going to have to pay quite a lot extra for this birth. I remember checking this link for all the midwives in Cape Town and some did practice in the Northern suburbs, but perhaps as mentioned, they only do homebirth, I am not sure.
www.capemidwives.co.za/hire-a-midwife.php
It is worth checking the link, perhaps there is someone who can advise you on what best to do in the Northern suburbs. Otherwise consider driving to Vincent Pallotti? All of the doctors there (Dumbrill, Richardson, Searle, Hinz(she is German!)) are pro natural and you don't actually need to have a private midwife if you can't afford to pay for both! Something I did not know at the time