To expand on the tritium point, only a small amount of tritium (a few dozen kilos) exists on the planet at any given time because it has a half-life of only about 12 years. In North America, the primary civilian source is a byproduct of the CANDU reactors in Canada, and that's only a few kilograms per year. The other major source, used for supplying tritium for US nuclear warheads, is a fission reactor in Tennessee where special rods are irradiated over the course of months to produce a few hundred grams of tritium.
To have enough tritium for fusion, effective lithium blankets need to be developed that capture neutrons and produce tritium (Li-6 + n = He-4 + T) to be fed back into the plasma. To my knowledge, this has not yet been demonstrated, though work has been ongoing.