It is not available aftermarket. I wouldn't replace the Como fork. It is hard to find a
good and matching replacement fork for that e-bike. Not having the front shock also makes the bike more lightweight. The universal advice: inflate your Como tyres just to 50 psi (55 max) and you are well-off on the gravel. I know better as my specific Vado model came with the rigid fork and I can live with it easily.
You might replace the handlebars with the Baramind BAM Trek, the shock absorbing ones. Also, consider replacing the grips with Ergon GP3. The beauty of these grips is you can hold the bars by bar-ends as if you were driving a car. The hold can be very delicate and it makes the ride very easy on hands, arms, and head (hardly any vibration experienced). Since I ride long trips with such a configuration, you can trust me.
(With speed bumps it is better to stand on pedals for awhile).
Stefan in Brwinów at the Podkowa Leśna border