I think one possibility would be to offer anyone who buys supporter to pay one or two bucks extra as a donation. That money would be collected in a pool and at the end of every season (or once a year, whatever is easier to handle) given away in free supporter packages to selected users form countries with either low supporter numbers or low GDP.
I would certainly donate one or two bucks every once in a while if I knew that money would be used for a good cause and help the game.