Hi,
Richard sells a charger that matches the GEL batteries that he supplies, but if you're NOT using GEL batteries, there are alternatives.
I use a Tecmate 'Optimate 4' it does ALL type of lead/acid batteries (including gel), with auto detect. Better - it's DESIGNED to be left permanently connected without damaging the battery, so your Toylander is always ready to go. It is an intelligent device, and will in many cases recover previously 'abused' batteries. I use this for topping up garden tractor batteries - that's about the toughest use imaginable for a battery - and I get about 5 year's service from a battery.
These are the chargers that the 'classic car' people use to keep the batteries in their 'summer only' vehicles conditioned.
Available at about £40 retail. There IS a 24V version, but it's designed for industrial use, and is MUCH more expensive. If you want a 24V charger, go for Richard's item.
Phil