where do I buy a side kick phone in India , Chennai ??
You can buy sidekick phone from ebay.com or amazon.com . Do you want to buy unlocked or locked phone ? carrier unlocked phones are too expensive. So that, buy a locked sidekick phone from any of the online shop and unlock it from any of the 3rd party service providers like http://www.mobileunlocksolutions.com/sidekick/rs16wp8/ to unlock it . Because, locked phone and the unlocking cost is low when compared to unlocked phones . Once, you have unlocked your sidekick from sim/carrier lock, you can easily switch over from your current network to any other GSM networks .
I would try ebay india. I wouldn't buy it from anywhere else, because ebay has feedback and other ways to make sure you aren't getting scammed.