LAN Addict looks at the BT510 Bluetooth Mini Mouse and the BT009Si Bluetooth USB Adapter.

One of the biggest features, in my opinion, is the additional USB power supply. What this means is that, in the event your batteries die, you have the option of plugging in the included USB cable and connecting it to the BT510 for power. Yes, that means you are no longer wireless, but it also means that you can still use your mouse!

Bluetake BT510 Bluetooth Mouse and BT009Si Bluetooth Adapter