I think the ear is perfect, and perfect for the Halloweeners
And depending what you want out of the encounter, you could either just leave the players to talk/bluff/intimidate/fight their way out of it ("does the list say it has to be cut off? No? Fine, I'll come with you, you show them my ear, but you promise I walk out afterward")
... or you could have the gangers eventually say "We're taking one of your fragging ears, like it or not. It isn't like you would have ..." (something exotic enough, hard for the halloweeners to get, but that the runners have or could get -- although possibly valuabe enough that they would want to go with the thing to guard it)
... " a fragging working laser pistol."
... " an authentic '2063 Dunkhelzhein for president' poster"
... " a dragon who would come to the judging for our team."
... " a Hermes Chariot cyberdeck being pulled in a chariot by guys dressed up as Hermes, whoever the frag that is. Who comes up with drek these lists?"
... " an entire band, complete with amps and speakers, to cover Concrete Dreams greatest hits."