I like this charger you suggested scooter, however it states that it does not come with an AC adapter, which seems to be the norm (I have no idea why!), where would one go about finding one of those?

It's a DC charger, meaning you need a 12V power supply or run it from an old car battery. You just need to keep the car battery charged. The alternative is a 'mains' (110V here in the US) charger, which cost a bit more but you don't have to worry about the power source.