I might have created what you seek, but don't expect to much. I made it in 6 hours.
But see
http://laybit.com I think this is what you need.
Kind regards
Kris
Cool!
My recommendations:
1) don't have people specify "monthly budgets"... that's a relic of the old systems that bitcoin does away with. Instead, when someone clicks the Laybit button, a quick popup should ask how much to donate. I know I'd rather tip some people more than others.
2) Not thrilled with the name... I bet there's somethin better