The lab down the hall uses Tritium. My old night scope uses tritium. You can buy tritium florescent toys. Its rather low energy beta emitter.
The reason its gets highly regulated is that once you can get enough of it, ie grams worth. It becomes a very important addition to fission weapons. In short it makes fission weapons *many* times easier to make. Things like ITER and JET require large inventories of tritium. That gets a whole lot of pain WRT regulation.
If something like the DPF can use a very small inventory, regulations are not so prohibitive. I have not idea of how much you would need. But it could well be at the quantities that attracts lot of regulation.
