This is going to rub a lot of people the wrong way as unethical, but the best way to incentivize organ donation is if the donors get paid a market price for the organ. The donor is giving up a valuable piece of their body, taking time and large medical risks in surgery, and likely reduced life expectancy.
If you walk through the current process, everyone in the donation gets paid -- doctors, nurses, hospital, pharma -- except the donor.
There are a number of advantages of donors getting paid:
1. The supply market would increase dramatically. Thus many more people receiving organs who would have otherwise died waiting.
2. Heirs to people who have died young, with healthy organs could get paid for donating their organs.
3. Black markets would be dramatically reduced, since people in desperate need of an organ could pay in the open, rather than secretly paying a donor.
4. People without money can legally open a Kickstarter to raise funds for an organ donation.
Note Iran has partially done this, and the results have been very positive [1].