There's nothing particularly special about paralleling 2 Honda EU2000i gensets as all you're doing is combining one inverter's 120 vac output with the other. Honda offers their own custom parallel kit which is designed to avoid the possibility of accidentally shocking yourself. As you can see in this EU2000i wiring diagram this parallel cable kit also allows for a fuse to be placed between it and the receptacle outputs.
Electrically though you can achieve the same result by simply using a suicide cord (Male 15 amp plug > Male 15 amp plug) to connect the 2 gensets together. However, use caution as it's called a "suicide cord" for good reason. :E