@query1000, as you are already in contact with Purism, why not to ask directly if you could buy one MM-M50D M.2 modem card (or some other if technically …) and send it to them (of course you need to coordinate everything before with your correspondence) to check it for you … if it is compatible with the Librem 5. If I were in your situation I would invest in such purchase of one M.2 card for Japan usage (only), send it to Purism (if they say yes) and even if it shows as not adequate you know where you stand with it. But if the answer from Purism, after testing your M.2 modem card, comes as positive than you should commit yourself to buy one Librem 5 (with your M.2 modem card). Query1000, this is just my thought that you might try to work around … or otherwise you might be relatively long looking where to find and upgrade a used Librem 5. You will need some patience anyway!