Son wants to "sponsor" a missionary.?

I would personally recommend just thinking of a country or a cause that you feel strongly about and just googling it with "missionaries" included. I apologize, I do not have that much knowledge of specific organizations. But the best way, generally, to find missionaries who could use the money is to ask your friends if they know anyone who is doing mission work, or of anyone who is. There are some organizations who can put you in contact with specific people though. I could put you in contact with some friends I have teaching bible studious and such in China. If you want to send me an email I would be happy to do so. It is a married couple with two young children (one just born this year!)