Where can you buy castor oil to induce your labor?

You should not induce labor. Only a qualified obstetrician is knowledgeable enough to be the one that jumpstarts the process. If your body isn't already in labour, there is a reason for this, probably because it isn't ready. Please don't take this into your own hands. Castor oil often just causes vomiting and diarrhea, which isn't something you want during labour. It is also proven not to be effective at inducing labour.