You can find sufficient hydrogen in a hydrogen generator. A good hydrogen generator will be a self-sustaining and fully automated, which utilizes an ocean's current and water to produce vast amounts of hydrogen. Here, hydrogen is exported plus the oxygen, which is not consumed by the life support systems.
Sufficent for what? If you need large amounts, you can purchase them from a supplier of industrial gases, who should be found in your regional yellow pages. Small amounts you can try to make yourself. Keep in mind that handling hydrogen is dangerous, so try not to blow yourself up.