If you can't find a BT mouse you like, the Logitech NanoVX is pretty slick, and the USB adapter only sticks out ~2-3mm from the USB port.
I know a lot of people don't like the mighty mouse, but I use it every day at work, all day, and I love it. The integrated on/off switch that doubles as a dust cover is a nice touch, and the scrollball works well if you keep it clean.
Get the Logitech V470. I've had mine for a while and is a damn good mouse.