I also went with a true sine wave inverter. Two computers I've had wouldn't work at all with a modified sine wave inverter, and one of them the "brick" power supply/charger got very hot.
FYI, all external computer power supplies are made with switching power supplies, at as far as I've seen. Doesn't make sense to not use a switching power supply. Some are more sensitive to sine wave actual shape.
I also think the best option is a 12 volt car charger. They're not very expensive. I have car (12 volt) chargers for all my portable computers. Save space, weight
, and efficiency. Every time you go from on voltage to another you loose at least 5% in heat. Going from 12 volts DC through an inverter to 120 Volts AC is a 5% loss in power, then going from 120 Volts AC to 19 Volts DC is another 5% or more. So you're using more battery
power to heat two devices when going inverter to power supply than when you go through just one.
Another little trick, when you go someplace in the tow, use that travel time to charge your electronics. Saves your house battery
for stuff needed in the trailer.