The Black Clinics are one of the most underground organizations in Midian. If you need something taken care of and you don't have the credits, want the attention, or want to answer a bunch of ethical questions from a doctor, you seek these guys out.
Nobody knows who runs them in the end but they do all sorts of surgeries and even dabble in cybernetic and even the odd bionic procedures. It won't be pretty and it won't be cheap, but many times it's the only recourse for some people at the very end of rock bottom.
It's rumored the Biomechs go to these people for repairs. It's rumored that some people who walk in never walk out, harvested for parts in some grand, mad experiment. You'll never know where it is until you get there and if you go back it's just as likely to be an empty building as full of derelicts who swear they've been squatting for weeks.