You can probably get switches from Nissan, but I doubt that local dealers would stock them since failure is rare. The older LEAFs had a panel with blank spaces where switches could be added and they were a standard size available from multiple sources. The newer cars don't have that panel so I am not sure where you would mount a switch to make it look like original. Also, most of the switches in the newer cars are momentary contact and you probably want an on/off maintained contact switch for your application. If there are any car recycling centers (junk yards) near you, you might be able to get a switch from a wrecked LEAF.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL Plus purchased 8/10/2019