Mens visual kei help?
 

so my boyfriend wants to go visual kei and I'm supposed to help him find everything. But I wanted to know what kind of casual t-shirts would go under like the awesome jackets and vests? Also where can I find said shirts? Would it just be like band Tees?

I think your best bet would be EBay as there are various vendors there that import Visual Kei styled clothing directly from Japan.

Here are some links that have been referenced before, but you should check with the dealers via email before you order to get details on exchange policies, shipping costs to LA and availability:

visual kei items - Get great deals on Outerwear, Shirts items on eBay.com!

Little Chili Shop items - Get great deals on Pants trousers, Long Sleeve items on eBay Stores!
gothic lolita punk pants items - Get great deals on NANA Rocking shoes, enginering boots items on eBay Stores!
Wai1222 CoLLecTiOn items - Get great deals on dress. one piece, skirts items on eBay Stores!
REFUSE TO BE USUAL items - Get great deals on PUNK ROCK JROCK, GOTHIC LOLITA items on eBay Stores!

As for styling suggestions, you might want to try these sites:

Visualive (Japanese Only)

Visual kei style (this applies mostly to girls)