Is there anything I can get from the grocery store or drug store for my steatorrhea until I can see a doctor?

Not really. If you truly have steatorrhea (fat malabsorption) the cause needs to be addressed. Pancreatic insufficiency or small intestinal diseases would be the most likely causes. Symptomatically you can avoid eating fat and this would help until you are evaluated. Steatorrhea is fairly uncommon and without seeing a doctor I am not sure how you could get this diagnosis.