Is there a black market for human organs? Yep. Would you allow this in libertarian 'world'?
Absolutely. It would solve the problems we have today with organ shortages. If I don't own my body, who does?
Right now there is a black market in human organs because government dictates who gets what organs, regardless of what the donor wishes.
Willing donors could sell (or bequeath) their organs to whoever they like. Since it would be illegal to initiate force or fraud, organs could not legally be stolen from the unwilling.
There would be an open market for donor organs, and the black market for donor organs would disappear. There would still be a black market for stolen organs, but it would be illegal.