I'd pick something like this:

https://www.amazon.com/Schumacher-SC1301-Automatic-Battery-Charger/dp/B0756P7Q48/ref=sr_1_3?crid=2YWY7Y3UCKNEY&dchild=1&keywords=sc1200a%2Bbattery%2Bcharger&qid=1588780805&sprefix=sc1200a%2Caps%2C206&sr=8-3&th=1

In fact, I've got something like that in my garage now.

You want a 6 to 12 amp charger if the battery is low enough to actually need charging. You can get a 2A "trickle" charger for cheaper, but those are not great for when the battery is actually run down and needs to be recharged.

In general, the cost difference between 6 and 10 or 12 amps is so small that you should get the bigger of the two. i.e. on the charger I linked, there is a 6A and a 10A configuration, and the difference between the two is only five bucks, so it's worth picking the more powerful charger.

Now, It's also possible to spend more money for a bigger charger - but those typically won't actually *charge* any faster, they're just designed to produce a temporary surge that you may be able to use to "jump start" a vehicle. Not worth the extra cost and bulk IMO.

This will work on any car, not just a leaf, but it'll also work on any EV that has a standard 12v "house" battery.