I recently bought one of these at Bed, Bath & Beyond and got 20% off with a coupon that my wife had. I bought the one that comes with a Razr adapter (mini-USB) so that I can charge my phone and BT headset. Then I ordered the Nokia adapter directly from Turbo Charge here for about $5 delivered. The TurboCharge is small and uses a single double-A.
I can't help but think the TurboCharge is hideously expensive: I bought my emergency charger (for 4 AAA's) for 2.5 euro; granted, it's made out of the cheapest black plastic, but it also came with six adapters.
Granted, I did buy my spare wallplug charger for more than the price of the TurboCharge (EUR 19.95), mainly for the Nokia mini adapter, but that one came with a collection of adapters as well (including mini-USB).
I'm now cannibalizing a couple of those adapters to make an extension cable for the AAA-charger, so that i can use the 770 while it's charging.
