Hi
Hi
You are right. The easiest thing to do is to buy a 12v laptop charger. This will charge your laptop from the 12v DC system you already have, and not required the inverter.
You are also right about the alternator. When the engine is running it is generating loads of 12v power, so use this to charge things.
I’d highly recommend a split-charge relay to charge you leisure battery from your engine battery.
When your engine is running you can charge you laptop using the 12v charger still.