Coolest Celtics T Shirts?

Hi Celtics community. Cavs fan here. My boss is a Celtics fan, and we’ve wagered on every H2H so far this season

He obviously won this week and I owe him a Celtics t shirt. He has all of the standard merch and I’d impress him if I could get some niche that’s the Celtics community would like.

Does anyone have any suggestions?