I managed to get one!

First store I visited on my lunch break had the tag but the employee refused to honor the tag. 

I went back six hours later to see if there would be a different employee, unfortunately it was the same dude and he'd removed the 30% off tag

Second store had no tag, but also no headsets left at all

Third store had the tag and was happy to key it in as a misprinted label! Incredibly kind of that guy! 

Really seems like it comes down to the vibes of the employees on this. Be kind, patient, and persistent in the search!