You asked about Foongus plushes--currently, they're officially distributed only in Japan. Your best bet is an import shop. I don't know where they exist in your area, but if they cover Japan (and there are a lot of import shops that pretty much import ONLY from Japan), there will be Pokémon plushes.
There are so many different Pokémon plushes, however, that if you find one, you're not guaranteed to find Foongus. Check their shelves, and if you can't find it, ask a worker. That is, if you can find an import shop--they tend to be concentrated on the Pacific coast. If you live far away from the Pacific Ocean, it'll take some effort to find one.