Not true, I have used one on 240v, it does just fine. Here in the states, we just make a conversion plug and go, there aren't even any settings that require changing. These chargers are very flexible for input voltage and frequency.
Either charger will work using 240v, just install the correct plug. It's that simple, no inverter/converter or any other expensive contraptions required.
I think it's fair to say, someone did something just a little bit wrong...
And I think bubblegum and duct tape should suffice to repair, no need to go overboard with super glue.
I had a chance to go explore around the Washougal MX park property, and ride some awesome single track. Sadly I was the only Alta to make an appearance.
The Predator 9500 inverter unit should do what you want, with some capacity to spare. And building an inexpensive splitter cord should be well within your abilities.
But I'm sure you already know this...
Wives are funny that way sometimes... mine forced me to buy a KTM so when we go camping we don't have to take "that huge generator" along every time. So the Alta only gets to play around closer to home, could be worse.