Ah, the mist clears a little. I presume you're wanting to charge your model batteries whilst you're out at the pond or wherever. If so just google li ion leisure batteries, there's plenty of choice with a range of ah capacities. If you're charging at home then obviously you'd use a power adapter or get a charger that runs off the mains electricity.
For a better answer you need to provide more facts, i.e. Battery type, capacity and main usage.
I'm pretty typical, i have a main battery for a model and a couple of spares, i charge at home with a modern smart charger plugged into the mains before sailing. When i return i plug the batteries back into the charger to put them at storage voltage.
I hope that helps a bit.