Gentex is the brand and they supply mirrors for many auto brands. You can tell since their name is often embossed on the mirror somewhere. Or perhaps just by looking - I think there are only 2 or 3 companies that make these mirrors. You can check ebay to find tons of them, probably.
You can tell if the mirror is powered since if it is, there will be wires running from the mirror up the windscreen to the bottom of the headliner. Usually, these wires are inside a small plastic raceway that lies against the glass behind the mirror. At least that is the setup on my 2017 Leaf. On some cars the mirrors mount directly to the roof so the wires may not be visible. I don't have a Gen2 so I don't know how the mirrors are mounted on those.
FWIW, I bought Gentex GNTX-453 mirrors from a local junkyard. There are many different brands and models that use the same mirrors and the differences are whether or not they have HOMELINK, compass, temperature, etc. These extra features use more wires but IIRC there are basically just 2 different pin-outs for the wiring connectors, which are also very standardized.