A pannier is a basket, bag, box, or similar container, carried in pairs either slung over the back of a beast of burden, or attached to a bicycle or ...
i didn't know, either, had to look it up :biglaugh:
most of us would just know them as saddle bags or just plain old "bags"...
JC Whitney has some, but it was something i just happened to notice - i'm not a bag guy so i don't know if the ones they have are attractive or useful :ummm: