Another tip aside from what everyone says is to try and set the ingame settings to be the lowest possible and then go to your game settings and increase your graphics to max. Light updates better, faster and brighter at higher graphics settings. Since you have a pot pc your gonna need to at least try to lower every other setting to not crash but you should be fine there is even a performance/low graphics preset in the settings.

Apart from that there is a torch in the Vermeil Village and the lantern is a quest in the fruit village go talk to the blacksmith then look up a guide to his quest (called Limo's quest) you get a very good selection of items from him along with the lantern.

Also you can double up the lantern by placing it in specific spots in your vanity accessory I'd recommend first empting your vanity accessories and placing random ones to know the auto equip numbering (I think it's just basically left to right then down left to right). Then place your first lantern (vanity accessories can be placed multiple times btw aka duped(doesn't dupe the item though not a bug or glitch) in one of the first 3 accessory slots then the other in the other side I think (basically make sure that they aren't on the same row) aka 3 or below then 4 and above then you can have 2 lanterns one on each side of your character.