i found 1 rare candy and kept 'mass cloning' as i call it.
but you can find one on route 117 (i think) near where the registeel cave is? there is a pool of water with some berry bushes near it. anyway, its near there somewhere (i cant remember exactly)
and also there is one in the dewford cave, you need the mach bike though, and its in there somewhere.
sorry my memory isnt too good, but its been ages since i last found a rare candy.
The White Stripes make the best music ever! They really do xD