The only YouTube how-to video I can find for upgrading Leaf trickle charger EVSEs is for switching from a 200v to 240v transformer in 2012 hardware. Looks like the 240v transformer he installs is only about 7 USD, but I assume that my 2013 U.S. spec 110v EVSE would probably require very different retrofitting than just the transformer?
https://youtu.be/IXz5bDEiIi0
Thanks for the tip on the EVSE for sale, jjeff. I just realized that the 30% U.S. federal tax credit for EV charging equipment has been extended retroactively through 2020, so I may just bite the bullet and go with a Clipper Creek HCS-50, Chargepoint Home Flex, or JuiceBox 40 and be set for a while (even though my current Leaf obviously can't charge with more than 27A). Not very usable as portable equipment, of course, but at least there are a number of Nissan dealers and L2/L3 chargers in my area.