It seems that you don't have the latest OS X 10.1 Installation disc.
The fact is here -
As Apple releases Mac OS X 10.1, there is actually 2 version of Installation disc available. The first available, the publically know as build 5G64, does not contains Chinese Input methods.
The second available (at least in Hong Kong) is know as build 5J34, which contains all Chinese Input methods.
The components missing in the first available version of Mac OS X installation disc cannot be downloaded from software update or Apple web site. Even after you have installed 10.1.1 update, the options is still not available.
The solution is to get a new OS X Update CD which is 5J34. If you are in Hong Kong, you can get it easily in Hong Kong's reseller. Just take one of the OS update coupon with you and ask them for the disc. It should be free.