I am actually just dealing with this question myself. From what I have read in the Kona forum and other forums related to the factory EVSE or "Granny Charger" it is set up to deal with 12 amps at either 120 or 240 volts. So I am looking at putting either one of two different options together.
1) a female 120v standard plug to plug the granny charger into which then has two male ends off the other side to which I can connect to two separate 120 v wall plugs from separate legs if a home's electrical panel. If each 120v feed is wired to a separate leg of the 120 v female end with the grounds wired together and to the neutral of the opposite males, you should get 12 amps at 240 volts which should double the speed of charging when visiting my in-laws as an example, who do not have a dedicated 240 outlet in their garage.
My other option:
2)
Is to feed from my in-laws panel to the garage with 240 from their panel and install a 15 amp 240 volt outlet. Then wire an adapter cable, again with a female standard 120v outlet for the granny charger to plug into and then with a 240v 15amp connecter on the other end, again feeding both legs of the charger.
The granny charger is only capable of charging at a maximum 12 amps, but it can do so at 240v which makes for closer to 2.8 kw instead of the glacially slow 1.4 kw you get from a standard 120v outlet.
I know there are places you can get these adapters, but honestly, if you're at all comfortable with electricity I would suggest getting the parts and making one yourself. You just have to make sure whatever plugs and wiring you use is rated for up to 250 volts and is sufficient for 12 amps CONTINUOUS! Last thing anyone needs is a melted cable and the possibility of a fire. All connections need to be solid and you should be fine.
I'm definitely leaning more towards my second option as it is the one that seems the most "right way", which is how I generally prefer to do things.
At home I have a proper EVSE which is hard wired and supplies 6.8 kw happily all day long. I'm just thinking about when I'm not at home for faster charging.
Hope that helps, sorry it's very "wordy".