I sadly don't have any pictures of these shirts in the wild, but here are the shirts I got for my spectators to wear in Portland and beyond.
Happily they can function as shirts for future events, even to support other Bumps in their spectator-worthy adventures. I ordered them from CustomInk.com and I really thought they were good quality, although still on the pricey side for a t-shirt. They would have been cheaper if I'd bought more of them, but I can always order more later, and I'm doubting the demand will be extreme. I went for the cheapest of cotton t-shirts, although hoodies would have been a better bet given the weather. Even my dad wore one. It was was super cute on him. I think I'll make him my future model.