Prisoners (ala Larry Niven's "The Jigsaw Man").

Hospital brokered Markets (if we ever legalize sales).

tldr; Bre Pettis via Erin Griffith's answer: 3D printing.

Another answer is in the movie "Never Let Me Go", one of the most bleak movies ever made.

Grow them in vats? There was a story about lab grown vaginas a while ago; hoping this happens for organs too soon.

Police shootings.

Motorcyclists.

Pedestrians.