They normally use aluminium oxide as the dielectric rather than ceramics or polymers. They have larger values and poor electrical characteristic and are also polarised which means they have to be put in the circuit the right way round.
Nice circuit by the way, I like the way they use the LED as a diode in the voltage doulber, it'll probably work for white, violet and blue LEDs if a 3V battery is used rather than a 1.5V cell.