The author built the circuit on a piece of experimenting board, using parts
available from the closet.
The fact that it was built from parts readily lying around makes, for example, that MOSFET T1 is a rather strange type. In principle any P-channel MOSFET can be used for this, as long as it can cope with the peak current of about half an amp. The coil L1 does not have a critical value either. The author's coil comes from a backlight-inverter, but any slightly hefty coil will do. If the 20-V power supply is actually in the vicinity of 20 V, then all is well.
The printer, as built by the author:
It does its job quite well. It's possible to print on paper and whiteboard...
....but printing on a nice pint of Guinness is possible too:
(No guarantees on the drinkability of the beer afterwards, btw)
...and even printing on water is a possibility:
Although the ink fades away in half a minute, unfortunately: