Where can you find sodium for the human body?

If you mean elemental sodium, you can purchase it from a chemical supply house. If you don't know what that means or how to proceed from that clue, you have no business having it; sodium is a hazardous material.

If you mean sodium ions in your diet, it's actually much more difficult to AVOID getting sodium; most foods contain more sodium than your body needs (and, in the case of many processed foods, far more than is healthy).