That's a very broad question. This forum is as of yet quite small, and it wouldn't take much work to go through the pages and take note of the various sites mentioned - there have been at least a few. I doubt you'll find precisely what you like as at first glance I can tell you that the more frequent posters do not wear those kinds of shirts. In any case you can certainly find names and websites for lots of other things that we deem "cool." Good luck and welcome to the forum.
My eyes, my eyes. Seriously, as well as the sites mentioned, you can get this crap at, say kleptomaniac.com, Atlasclothing.com, or guyshop.com. I would strongly recommend that you do not do so though. This look is best described as "Tacky gay clubber". If that is what you are going for, by all means. But in my opinion, only the last example is even remotely wearable. The first example looks particularly bad. Please, please, do not buy something like that.
I guess this would be essential wear if you plan to work as a hairdresser and your name is Armand (no disrespect to truly trendy hairdressers around the world).
Watch it buddy. Armand is actually a black ops undercover dude deep undercover with Hollywood's much spoken of "Gay Maffia" and is as skilled in jiujitsu as Steven Segal. So watch yourself. He likes his ribbed black shirt with swirls.