All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no objection for a Muslim to buy a bodily part to be transplanted to himself or to somebody else provided the following conditions are met:
1- One should be in dire need to this organ; i.e., to save life or to activate some damaged part.
2- Transplantation should be the only medical means for the treatment of such an organ.
3- Success of such an operation should be mostly proved.
Islam set such rulings just to safeguard the human being and to honor him, and as an obstacle in the face of those who trade in human organs. It is a Divine Sharee'ah.
For more benefit on organ donation and its conditions, please refer to Fataawa 86647 and 323434.
Allah knows best.