Hot Topic has a pretty large selection of retro Nintendo shirts and other assorted stuff. Drawback is most of it is NES era and rather... well, they're just ing stupid.
A lot of that stuff on that link above is the same stuff you'll find in Hot Topic, Target, Kohl's, Mervyn's, etc. The shirts at Target generally run about $10 or $9 when they're on sale which is like once a month.