This is mainly for my work laptop, but my 3DS and possibly Switch will also get charged this way. What do I need to buy? I’m assuming a full step up converter is necessary. But most of the ones I’m seeing plug into US outlets because they are powered devices. Any suggestions?
A quick Google says the local hardware store ferretería will have what you need - voltage converter, one with built in USB would be ideal.
Switch chargers (and all Apple chargers if you’re using a mac) are worldwide 100-240V 50-60Hz, you only need to adjust the plug shape via a $2 converter.
I’m sure they’ll be available at the Peruvian airport for a bit of a premium.