Other sibling comments have mentioned using your phone or the Pasmo passport but I just got back from Tokyo last week and there's a machine selling the Welcome

Other sibling comments have mentioned using your phone or the Pasmo passport but I just got back from Tokyo last week and there's a machine selling the Welcome Suica, a time limited card where you lose whatever was left on the card, at Haneda and Narita. I picked one up when my flight landed and was able to top it up and use it all throughout my 3 week trip.