You'll certainly be able to get the battery somewhere in China. Quite where is a whole different question though!

I'm thinking that when you say you've got a Canon XSi you're not quite giving us the full details of the camera.... maybe an 'EOS 450/Rebel XSi' or something?

Have a look at the products page on Canon's Chinese site:

http://www.canon.com.cn/products/camera/index.html

If you can find your camera you'll have no problem finding the battery. If you struggle with the Chinese you can work from camera pictures (nice pun, eh!).

Equally China's default search enginge, Baidu, throws up enough results for the battery itself to suggest it's present in the China market:

http://www.baidu.com/s?ie=gb2312&bs=...-E5+canon&ct=0

The second result is probably even more proof:

http://www.smarter.com.cn/electronic...prod-72570154/

All up I wouldn't be too worried. China is a pretty impressive place when it comes to availability of the most unlikely things. You might not end up with a genuine Canon battery - but pretty much any decent camera store (and in Beijing there are lots) will be able to sort you out.

If you do get a genuine battery through an official outlet though - don't expect it to be cheaper than in the US - that's just not how China really works. Equally I wouldn't expect you to end up paying anything close to the RMB480 that site quotes. Bargain as best you can.

Have a good stay in Beijing. The Chinese are very much in anticipation of the Olympics and I'm sure you will be welcome - to quote from an e-mail I've just got:

Another exciting thing is that the Beijing 2008 Olympic games are coming.It's a great pride of Chinese people.You may know from TV that the great Bird Nest Stadium and Shui Li Fang
have been built for the Olympics games.
The environment of Beijing is also greatly improved.We Chinese people are
all working hard ,taking on a new look
to expect the arrival of 2008 Olympics.