There doesn't seem to be much out there really (maybe kinkmeme fic? I 'm not following any of them), which is a shame because I think Tony would make an awesome sub of the frustrating and bratty but totally worth it once he actually went down sort. My going theory about the relative paucity of fic in that direction is that it's really hard to imagine either character voluntarily raising the subject. When you're reduced to Tony snooping around Steve's internet history as the most plausible scenario it can start to feel like grasping at straws.