Let's face it, most of us use this stuff as a call to find other nerds. for example when a nerd says "I like your shirt" they really mean "YOOO IM IN THAT FANDOM TOO" so here are some good places to buy nerd mating calls:
Anime:
https://www.rightstuf.com/site/categories/merchandise/
Various:
http://thedailyfandom.com/best-sites-to-buy-nerdy-merchandise/
http://www.rockabilia.com/
Alt/screamo/punk/emo Band Merch
http://www.bandmerch.com/
https://www.districtlines.com/home
Youtubers:
http://www.redbubble.com/shop/youtube+t-shirts
Classic Rock:
http://oldglory.com/lp/search?c=MUS_11000&f=22281&gclid=COTus6mlzMICFSaCMgod9DoARg
Punk/punk rock:
http://www.hottopic.com/hottopic/Tees/MusicTees/PunkTees.jsp
Anime:
https://www.rightstuf.com/site/categories/merchandise/
Various:
http://thedailyfandom.com/best-sites-to-buy-nerdy-merchandise/
http://www.rockabilia.com/
Alt/screamo/punk/emo Band Merch
http://www.bandmerch.com/
https://www.districtlines.com/home
Youtubers:
http://www.redbubble.com/shop/youtube+t-shirts
Classic Rock:
http://oldglory.com/lp/search?c=MUS_11000&f=22281&gclid=COTus6mlzMICFSaCMgod9DoARg
Punk/punk rock:
http://www.hottopic.com/hottopic/Tees/MusicTees/PunkTees.jsp
SAMPLE: 5 Items from http://www.hottopic.com/hottopic/PopCulture/TV/DoctorWho.jsp
Doctor Who Her Universe TARDIS Costume Dress SKU : 1
$34.69
$25.88
American Horror Story: Freak Show T-Shirt
$20.59
$15.30
The Book Of Life Amor Pin
$1.99
$1.49