What can I by over-the-counter for anemia?

Depends on cause. Lots of causes for anemia; not all are nutritional. Deficiencies: folic acid-fruits, vegs, fortified flour b12- animal products (incl eggs), fortified vegan. Some people can't absorb dietary B12 well iron- animal and non animal sources. Common anemia-blood loss: menstrual, gi, urologic: poor absorption: celiac sprue chronic disease: above items not deficient "anemia": thalessemia: not realy anem.
Iron, folic acid. If your anemia is due to iron or vitamin deficiency, you can take over the counter supplements. Your family doctor can make the diagnosis and tell you what you need. You want to be sure you do not have more serious causes of anemia before self treating.