Im having a HUGE singles gathering at a rooftop bar next weekend. Around a 100 people. I dont want them to wear name tags, but i want to bring

A subtle identifier to let others know they are part of the group. Besides nametags, is there anything subtle i can bring for them to wear? Like cheap bracelets or something? Name some stuff! Because obviously other people at this place won't be part of it, so it'll be easy to approach people that are wearing whatever it is