Where to buy the Samsung Galaxy S2 Extended Battery in London?

[lsquare]

I'm referring to the Samsung Galaxy S2 Power Pack/Extended Battery. I know it can be purchased online, but I'm wondering where I can possibly purchase this in London, UK?

Thanks!

[Hardcore Til I Die]

Carphone warehouse or some kind of market stall would be your best bet, but whenever I've gone in CPW for handset-specific accessories they've always pointed me online. They tend to sell universal stuff. My local CPW isn't very big though, some of the bigger ones might stock them.