It's been a few years since the "Expert Mouse" was released, and there's still no "Magic Trackpad" equivalent on the Windows side. Still, the earlier Expert Mouse trackball have been pretty good for folks wanting an HID besides the keyboard. But it's been years since an updated design.

This version improves the scroll ring, but adds many more buttons and knobs, many of which are probably extraneous (imo).

Early users point to an odd "off-axis" placement of the main sensor which results in unexpected cursor movement when rotating at the north end of the ball, so may not fit your working style. But maybe worth the eyeball if you like your trackball.