The official Japanese Pokémon website has revealed the Monthly Pikachu Plush Dolls (マンスリーピカチュウぬいぐるみ) for April 2015 and May 2015. To celebrate Golden Week, a Pikachu plushie with a Koiking Koinobori will be available from April 11th, 2015 to May 15th, 2015. From May 16th, 2015 until June 19th, 2015, a Pikachu plushie with a raincoat and umbrella will be for sale. Both plushies cost 1600yen each and are available at all the Pokémon Centers.


Sources: http://www.pokemon.co.jp/info/2015/03/150327_p02.html and http://www.pokemon.co.jp/info/2015/04/150424_p01.html