there are only 4 piece (top left, top right, bottom left, bottom right).
there is no secret of getting them to drop, sorry (I think I wond up with about 15 top rights and no bottom rights at one point),
Yes you can get them from other players (highly suggested since you are having such an issue getting one..). You can ask around kamadan for them, or gtob, they should be pretty cheap--you might also do a search here in ventari's to see if anyone is currently selling them.
where is the 'all you can eat' cookie bar?