Bob’s Cycle Supply is a gem of a shop for motorcycle parts and accessories. They seem to specialize in motocross, but they also have street bike goods. I think they also sell stuff for snowmobiles and ATVs, but I just look at the street bike gear.
Bob’s is great because you aren’t just looking at a tiny selection of accessories that most motorcycle shops carry. They have more brands, more stock, and they even have their own line of lower priced gear.