Admittedly I am still using trackballs! If you can remember them, the Trackball explorer 1.0 from Microsoft to be precise :) And they are great to work with, Asia based Elecom will release a version that resembles that old Microsoft one a bit, the M-HT1DRBK Ohama.

The M-HT1DRBK Ohama will actually be wireless, using thr 2.4 Ghz band, but there also is a regular wired version called M-HT 1 URBK. These units use a gaming grade optical sensor, with selectable 500 / 1,000 / 1,500 polling speeds. The buttons left and right are based on proper Omron's switches, You will spot all eight buttons including two side buttons, and scrolling left and right. You can assign functions the buttons using a software utility.

The unit dimensions are W 114.7 × D 181.9 × H 57.2 mm. The wireless model to be capable of working 534 days maximum with x2 AA batteries and low usage (no clue how they measured that though), and the wired model has 1.5 m cable. More info here (you'd probably need to translate though).

Elecom to release M-HT1DRBK Ohama wireless trackball