Jim Horton wrote...

Interesting that there weren't more responses.

I'm a big user of eBay and AliExpress, and purchase lots of
high-current and high-voltage stuff, to supplement my pile
of unusual parts, but I'd not come across the items you found.

Well, I had some trouble with the 3055's. Too much arcing
at tripler output would burn them out quickly ...

MOSFETs are more robust than BJTs, in that they can handle
excess drain voltages, and simply go into a safe avalanche,
the same as a zener diode (however the breakdown comes with
ns response times, so the wiring must be low inductance).
MOSFET gates are vulnerable, but if they're driven with a
serious gate-driver IC, with low-inductance wiring, they're
quite robust. The issue is high RF-frequency during arcing.


--
Thanks,
- Win