They're just generic AC motors held against the rim, as simple and cheap as it gets. Nowadays I'd add a basic voltage regulation circuitry to get a stable 5V DC out of it.
You'll spend more time futzing with one of or dealing with weather-related failures that you would have saved more time charging a pile of batteries before every ride.
I have rigged all kinds of rubber contraptions to make them work better, I have made my own dynamos from old electric motors as a kid, and yet I have never in all those decades found a way to be sure they would work when I need them, never.
I recently bought a dynamo from what should be a good brand (dunno the name off the top of my head). Cost about 45 Euro's, not cheap. Just after a couple weeks, whenever I cycle through the rain my dynamo wheel would slip and I'd be fully without light. I thought it was not properly pressing the rubber of the tire. But I found that the wheel was just cheap plastic garbage, totally worn flat already. I guess capitalism flew by, enshittifying once more what was once good.
The old-school dynamo's were undestroyable iron casings, with an iron wheel with deep grooves. Now I am looking if I can find one of those again, to last me a lifetime.