I have compiled a list of sources for the elements that are available to the amateur chemist. Hafnium will be discussed here.
Hafnium is the first element after the long and boring series of rare earth metals are completed. (Whether you wish to purchase all of them is a matter of your decision, of course, but some of the very similar ones may be skipped.) Anyway, hafnium is a dense (more so than lead), silvery gray transition metal. It absorbs neutrons, making it a harmful impurity in zirconium nuclear fuel casings which must allow the radiation to escape. Therefore, many pains are taken to remove hafnium from zirconium. In most applications, however, most zirconium is mixed with hafnium and vice versa. Therefore, your cubic zirconia is probably also cubic hafnia. Hafnium forms rather low-melting tetravalent compounds; its chloride hydrolyzes in water to form an insoluble hafnium oxychloride, just like most tetravalent compounds. Hafnium is extremely corrosion resistant and does not dissolve in acids or bases. It can burn in air when finely powdered, though, just like titanium. Hafnium finds use in very high-melting alloys, such as those used in rocket nozzles.
In element form: Find a plasma cutter tip at a welding shop and cut off the copper end. You will see a small cylinder of hafnium metal in the center.
In compound form: Cubic zirconia undoubtedly contains some hafnium, as well as most other sources of zirconium.
Here is my sample of hafnium. It is a plasma cutter tip tip.