I knew those pads (and companion steel rotors) from when I rode an 1100cc Suzuki motorcycle. To be fair, I used the bicycle pads in Seattle for only a year or two before returning to Austin where it's not so steep. Also I only ever had them on a pedal bike, not an e-bike (but I weighed 350-400 lbs during that time). Other than EBC, the only fully metallic pads I've used have been stock Avid and generic replacements (Jagwire, Clarks, etc.) So there may be similar or better pads around that I'm not aware of.
They're not wildly expensive-- like $17-18 online, $14 from this vendor:
Double Bolt Locking Mechanism provides added strength by locking the crossbar to the shackle on two sides\n Features 13mm ultra hardened steel shackles for maximum cut resistance\n Dust covers and vinyl coating protects the crossbar, shackle and cylinder from damage\n Includes...
carsoncitybikeshop.com
The main issue I have is hardly anybody carries them in stock at an LBS.