This Earphone

Buy.com has the Iogear 2.1 Wireless Bluetooth Headset - Class 2 for $42.80 - $25 Exclusive Mail-In rebate (Expires 10/31/2007) = $17.80 with free shipping.

Product description from Buy.com:

Freedom and Comfort. Enjoy true hands-free freedom with IOGEAR
lls through your Bluetooth enabled computers, detail instruction included in the package. To make your computer Bluetooth enabled, please purchase the IOGEAR Bluetooth USB adapter (GBU211)

Comfortable and lightweight: One of the smallest and lightest headset on the market and conveniently fits either ear.

Extra accessories: AC and USB charger allows charging from either AC source or from your computer.

Multifunction button: Call/answer button on the headset lets you conduct calls without having to pick up the phone. The IOGEAR Bluetooth Headset also supports several features built into many handsets, such as voice dialing, three-way calling, and mute.

Product link.