ham bone or ham hock - You are going for the smoked pork flavor. Okay to use 4 slices of bacon cut into 1 inch pieces. You can brown the bacon first and add the amount of bacon fat you feel comfortable with. Also, okay to use a small ham steak cut into cubes, or any cheap smoked meat.
large onion - or 2 small onions, white or yellow.
Also check my other recipe of black eyed peas curry in south Indian style. I really love the combination of black eyed peas and mushroom, as both are rich in protein and fiber and makes a satisfying meal with rice