You need this: the pin badge.

http://www.amazon.com/Steins-Gate-Makise-Kurisu-Cosplay/dp/B0111WWNUK/ref=sr_1_1?ie=UTF8&qid=1445402257&sr=8-1&keywords=steins+gate+pin+badge

I love mine. It's so very steins;gate yet it looks nice enough that I can wear it on my coat without it looking weird.