gdrago , there are some news of some sellers in ebay selling legit 4GB players. However, there are no reviews of anyone purchasing them so far.
Have a read in this thread, there is a post by "kerdu" of the supposed legit 4GB seller.
http://www.mympxplayer.org/4gb-mp3-m...e--vt3812.html
Hopefully kerdu does feedback into the forum of his/her experience with this seller and the authenticity of the 4GB capacity.
But since you are looking for a 2" screen player with 4GB, i can only think of the Meizu Miniplayer and Teclast T29 or C260 (with 2.4"). These are from reliable sources and can be purchased from the forum's sponser HouseOfDAP.com