Is this the correct battery for my GS100
http://www.bhphotovideo.com/bnh5/controller/home?O=&A=ShowProduct&Q=&sku=290022

Or do I want something else and who has the best deal.
Thanks

Yes IT is.

In ebay some guy from honkong was selling pana du21 battery for around 50 bucks.
I bought from him two of those, they are working fine. If you want you may try from ebay.