Posters of any of the album covers only exist in magazines by this point. On the other hand, if you can't get to buying those older mags and truly care about receiving a guaranteed official poster, use the Gorillaz webstore. There are also other popular posters of the Plastic Beach era like this one though I'm not sure how directly official they are. They seem like more of a licenced use by a poster distributer since the ones that directly come from Gorillaz typically don't get reprinted very often except for seemingly the Reject False Icons one which pertains to it never running out of stock since its release date alongside RFI, end of 2019.