Well the place I bought my Wammy's stuff from was Ebay but if you're looking for an actual shop then I suggest Forbidden Planet or some Manga/Anime Shop in your area. There is also this AWESOME shop in Paris that almost only sells Death Note stuff! That's not much help if your not there though! :D
I don't know...I want some Wammy's Boys stuff too...I think you could possibly get them from Amazon! I got ALOT of Pirates Of The Carribean stuff on there!!!