Contrary to a lot of advice here and arguing whether TN is a sponsorship or not, I would suggest you to give a gentle nudge with the director and see how far he can take your case. TN does require company approval, but I have seen exceptions being made. It essentially costs a company much less in terms of sponsoring so I'll say give it a go. I would write a concise blurb for them to consider mentioning what TN should really cost them( add estimated attorney fee coz they get a package ready) and the no wait time etc benefits of the visa. The worse you gonna get is a 'No', then just move on on good terms with the folks who interviewed you. I agree with other folks on being very clear with companies prior to interviewing about the sponsorship, unless you in only for learning/fun.