Custom form based on geo location

Hello,
I am currently making a site for a client and he wants to offer a free trail to people only from a specific location in the world. In this case its Hong Kong.

So people who come from Hong Kong should only be able to see a custom form where they enter their details to get the free trail.

I would highly appreciate it if someone could guide me to the right direction on how I can implement this in a widget. Is there a plug in for something like this ?

Cheers,
Vishal