Our internet searches have produced a Master Tow 77T (and 80T) and a Demco Kar Kaddy that look hefty enough to tow the 3800 lb Leaf with two down. Previously, I rented a Uhaul tow dolly, which worked fine. The Unity FX does really well towing, even across the Colorado mountains on I-70 and along SH-160. Any tow dolly ideas?
A quick search shows that the Demco (at least the Car Kaddy SS model) is considered a bit more deluxe and has a folding tongue for storage. There are many more brands out there and you’ll find a few on your local Craigslist. If you look at other brands I’d advise to get a swivel plate version (both of these are) and to look at ease of loading/unloading. Width can be important too but a Leaf is a small car so probably not an issue. For brakes, I like the ease of use of surge brakes (which is what I have) and you don’t need to modify your Unity with a brake controller. But if you get electric, you’ll need the controller installed.