Theoretically couldn't you take an electric car and put an off-the-shelf generator in your frunk and wire it up to charge the battery as you drive?
Even my really underpowered PHEV has a 65kW electric motor. No "off the shelf generator" can generate 65kW, in fact it would be a huge unit that could.
We could of course say - well, it doesn't need to match peak usage, it just has to charge the battery faster than it depletes - you still probably need around 20kW for steady motorway driving, and that's a pretty hefty generator.
Furthermore, the generator can run 24/7, but realistically you will at most drive ~6 hours a day. So for a leisurely road-trip this may be enough to avoid needing stops at charging stations