I think those little devices you plug into a wall socket then insert a repellant tab into are far more popular than coils these days. And the smell is nowhere near as noxious.

That said, if mosquitoes are a problem where your relative is staying, you can be almost certain the place is already equipped with the devices. If not, then everything you need to ward off the little critters is easily found in the city. No need to bring anything. Except long-sleeved clothing and long pants.