As far as I know, white caviar comes out every year, and it's had the silver HW for several years now. For some reason it's hard to track down - I think it's fairly popular. I couldn't find mine anywhere nearby - they sold out really quickly. I know a couple of other girls here were looking and having a hard time finding one recently.
This is probably a bad time to look in the stores for white since the fall colors are in stock - black, brown, purple and dark red mainly.
You can try the Chanel number, or maybe wait till next spring?