If you're worried about possible backlash from higher ups for not helping the boob, then document your interactions with them as well as the steps that you have laid out for them to follow and how receptive they were to it at the time. Also try to restrict as much of your communications with this person to email as possible. This way you have time stamped and forward-able evidence of their lack of cooperation. If your boss is already involved then give this person your action-plan to solve their problem via email and CC your supervisor (and or theirs if they're in a different department). Spotlighting this person will hopefully either make them do their own work, or get your boss to handle them going forward. At the very least, putting this issue on the radar of higher-ups will help you in the long run when this person inevitably gets called out for not working, because they'll most likely try to point a finger at you.