That is the real solution. Allow for the full trade and sell but only from actual businesses raising and harvesting the ivory. Just like free trade coffee, this business model would end up producing a glut of elephants. But it sounds so much more cool and caring if you make something illegal. You can’t be hip if you run a business.
Its also part of why Botswana is among the more politically and economically stable nations in Africa. I believe tourism is their primary industry and they recognize the value of their wildlife.