The structure of a junction field effect transistor seems to be very similar to that of unijunction transistor. Schematically, the main difference seems to be that the JFET is run wit back bias and modulates the impedance of the semiconductor channel while the UJT is also back biased but finally becomes forward biased as the as the emitter junction voltage increases. Typically, that is achieved by charging a capacitor connected to the emitter. The result is a regenerative build-up of carriers which quickly discharge the capacitor.
Are there any reasonably priced JFETs that can work as UJTs? What part numbers are there? Are there any precaution to use to prevent damage to the device?