3.3v to 12v wouldn't be to difficult to make happen, but what it would definitely be is kinda pointless. I've never poked around on the RF board, though I'd seriously doubt there is any 12v spot on there, and even if one exists it wouldn't be able to source any kind of current to do anything useful.
What are you needing a 12v source for exactly? I'd have to guess there is a lower voltage way to go about whatever it might be.