Nokia BL-5C battery is available across a few online stores. But since, the device and the battery are outdated, please check the stock status.
1. Snapdeal - Rs. 161 ( Appears to be discontinued).
2. Flipkart - Rs. 120 ( + Rs. 50 delivery charges).
3. Amazon - Rs. 230
4. Infibeam - Rs. 299 ( Looks like it is out of stock)
5. Rediff.com - Visit the link http://shopping.rediff.com/product/bl-5c-battery/
Authenticity of the battery cannot be guaranteed.
The battery is also available on Ebay, but I will not recommend buying from Ebay or Rediff.com as the quality is not trustworthy. Please note that this is my personal experience with these sites.