Update 2024/09/01: Sales of personalized Suica and PASMO has resumed, but this means you are not supposed to share your card, and refunding the card requires the person with the registered name to be present. For travelers, this can be inconvenient and therefore not recommended.
Even though the official sites and notices in stations are all trying to convince you that there is no way you can buy a PASMO and Suica right now, scaring all visitors away, there are still many ways you can buy one now.
Suica for Tourists: Welcome Suica
This is the officially recommended way, even though they are sold in just a few locations. Also, they expire after 28 days and you cannot refund the unused charged money inside, so I personally do not recommend this. For those working and studying, this is basically useless. You can check out their official sites for where you can buy them: Welcome Suica
Regular Suica: buy a 1-day pass
Even though the official website mentioned that only children and monthly pass Suica are still sold, 1-day passes can also be issued on a new Suica. So if your trip has a day that justifies using a one-day pass (e.g. if you live in the west side like Nakano, a round-trip to Kasai Rinkai Park is already worth the cost of the Tokunai Pass!), go to a black ticket machine (that sells monthly pass), and choose the option that issues a new Suica. Check the following video but choose the new Suica option instead!
After the one-day pass expires, you can load stored value into the card and use it like a normal Suica. You can go to a station staff and request that the writing on the card be erased too.
